Social networking sites and the Information we hand them

Excerpt from Facebook Privacy Policy:
The Information We Collect
When you visit Facebook you provide us with two types of information: personal information you knowingly choose to disclose that is collected by us and Web Site use information collected by us as you interact with our Web Site.

When you register with Facebook, you provide us with certain personal information, such as your name, your email address, your telephone number, your address, your gender, schools attended and any other personal or preference information that you provide to us.

When you enter Facebook, we collect your browser type and IP address. This information is gathered for all Facebook visitors. In addition, we store certain information from your browser using "cookies." A cookie is a piece of data stored on the user's computer tied to information about the user. We use session ID cookies to confirm that users are logged in. These cookies terminate once the user closes the browser. By default, we use a persistent cookie that stores your login ID (but not your password) to make it easier for you to login when you come back to Facebook. You can remove or block this cookie using the settings in your browser if you want to disable this convenience feature.

When you use Facebook, you may set up your personal profile, form relationships, send messages, perform searches and queries, form groups, set up events, add applications, and transmit information through various channels. We collect this information so that we can provide you the service and offer personalized features. In most cases, we retain it so that, for instance, you can return to view prior messages you have sent or easily see your friend list. When you update information, we usually keep a backup copy of the prior version for a reasonable period of time to enable reversion to the prior version of that information.

You post User Content (as defined in the Facebook Terms of Use) on the Site at your own risk. Although we allow you to set privacy options that limit access to your pages, please be aware that no security measures are perfect or impenetrable. We cannot control the actions of other Users with whom you may choose to share your pages and information. Therefore, we cannot and do not guarantee that User Content you post on the Site will not be viewed by unauthorized persons. We are not responsible for circumvention of any privacy settings or security measures contained on the Site. You understand and acknowledge that, even after removal, copies of User Content may remain viewable in cached and archived pages or if other Users have copied or stored your User Content.

Any improper collection or misuse of information provided on Facebook is a violation of the Facebook Terms of Service and should be reported through the Help Center.

If you choose to use our invitation service to tell a friend about our site, we will ask you for information needed to send the invitation, such as your friend's email address. We will send your friend an email or instant message in your name inviting him or her to visit the site, and may send up to two reminders to them. Facebook stores this information to send invitations and reminders, to register a friend connection if your invitation is accepted, to allow you to see invitations you have sent, and to track the success of our referral program. Your friend may contact us through the Help Center to request that we remove this information from our database.

Facebook may also collect information about you from other sources, such as newspapers, blogs, instant messaging services, and other users of the Facebook service through the operation of the service (e.g., photo tags) in order to provide you with more useful information and a more personalized experience.

By using Facebook, you are consenting to have your personal data transferred to and processed in the United States.

Sharing Your Information with Third Parties

Facebook is about sharing information with others — friends and people in your networks — while providing you with privacy settings that restrict other users from accessing your information. We allow you to choose the information you provide to friends and networks through Facebook. Our network architecture and your privacy settings allow you to make informed choices about who has access to your information. We do not provide contact information to third party marketers without your permission. We share your information with third parties only in limited circumstances where we believe such sharing is 1) reasonably necessary to offer the service, 2) legally required or, 3) permitted by you. For example:

Your News Feed and Wall may aggregate the information you provide and make it available to your friends and network members according to your privacy settings. You may set your preferences for your News Feed and Wall on your Privacy Settings page.
Unlike most sites on the Web, Facebook limits access to site information by third party search engine "crawlers" (e.g. Google, Yahoo, MSN, Ask). Facebook takes action to block access by these engines to personal information beyond your name, profile picture, and limited aggregated data about your profile (e.g. number of wall postings).

We may provide information to service providers to help us bring you the services we offer. Specifically, we may use third parties to facilitate our business, such as to host the service at a co-location facility for servers, to send out email updates about Facebook, to remove repetitive information from our user lists, to process payments for products or services, to offer an online job application process, or to provide search results or links (including sponsored links). In connection with these offerings and business operations, our service providers may have access to your personal information for use for a limited time in connection with these business activities. Where we utilize third parties for the processing of any personal information, we implement reasonable contractual and technical protections limiting the use of that information to the Facebook-specified purposes.

If you, your friends, or members of your network use any third-party applications developed using the Facebook Platform ("Platform Applications"), those Platform Applications may access and share certain information about you with others in accordance with your privacy settings. You may opt-out of any sharing of certain or all information through Platform Applications on the Privacy Settings page. In addition, third party developers who have created and operate Platform Applications ("Platform Developers"), may also have access to your personal information (excluding your contact information) if you permit Platform Applications to access your data. Before allowing any Platform Developer to make any Platform Application available to you, Facebook requires the Platform Developer to enter into an agreement which, among other things, requires them to respect your privacy settings and strictly limits their collection, use, and storage of your information. However, while we have undertaken contractual and technical steps to restrict possible misuse of such information by such Platform Developers, we of course cannot and do not guarantee that all Platform Developers will abide by such agreements. Please note that Facebook does not screen or approve Platform Developers and cannot control how such Platform Developers use any personal information that they may obtain in connection with Platform Applications. In addition, Platform Developers may require you to sign up to their own terms of service, privacy policies or other policies, which may give them additional rights or impose additional obligations on you, so please make sure to review these terms and policies carefully before using any Platform Application. You can report any suspected misuse of information through the Facebook Platform and we will investigate any such claim and take appropriate action against the Platform Developer up to and including terminating their participation in the Facebook Platform and/or other formal legal action.

We occasionally provide demonstration accounts that allow non-users a glimpse into the Facebook world. Such accounts have only limited capabilities (e.g., messaging is disabled) and passwords are changed regularly to limit possible misuse.
We may be required to disclose user information pursuant to lawful requests, such as subpoenas or court orders, or in compliance with applicable laws. We do not reveal information until we have a good faith belief that an information request by law enforcement or private litigants meets applicable legal standards. Additionally, we may share account or other information when we believe it is necessary to comply with law, to protect our interests or property, to prevent fraud or other illegal activity perpetrated through the Facebook service or using the Facebook name, or to prevent imminent bodily harm. This may include sharing information with other companies, lawyers, agents or government agencies.

We let you choose to share information with marketers or electronic commerce providers through on-site offers.

We may offer stores or provide services jointly with other companies on Facebook. You can tell when another company is involved in any store or service provided on Facebook, and we may share customer information with that company in connection with your use of that store or service.

Facebook Beacon is a means of sharing actions you have taken on third party sites, such as when you make a purchase or post a review, with your friends on Facebook. In order to provide you as a Facebook user with clear disclosure of the activity information being collected on third party sites and potentially shared with your friends on Facebook, we collect certain information from that site and present it to you after you have completed an action on that site. You have the choice to have Facebook discard that information, or to share it with your friends.

To learn more about the operation of the service, we encourage you to read the tutorial here. To opt out of the service altogether, click here.
Like many other websites that interact with third party sites, we may receive some information even if you are logged out from Facebook, or that pertains to non-Facebook users, from those sites in conjunction with the technical operation of the system. In cases where Facebook receives information on users that are not logged in, or on non-Facebook users, we do not attempt to associate it with individual Facebook accounts and will discard it.

If the ownership of all or substantially all of the Facebook business, or individual business units owned by Facebook, Inc., were to change, your user information may be transferred to the new owner so the service can continue operations. In any such transfer of information, your user information would remain subject to the promises made in any pre-existing Privacy Policy.

When you use Facebook, certain information you post or share with third parties (e.g., a friend or someone in your network), such as personal information, comments, messages, photos, videos, Marketplace listings or other information, may be shared with other users in accordance with the privacy settings you select. All such sharing of information is done at your own risk. Please keep in mind that if you disclose personal information in your profile or when posting comments, messages, photos, videos, Marketplace listings or other items , this information may become publicly available.