When it comes to sharing your information with third parties, the following paragraph sums up the Facebook policy quite nicely:
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.
Of course the use of all of these Facebook Applications complicates matters somewhat because these applications often take advantage of information contained in your profile and are developed by third party developers so you really need to be mindful of who these developers are and whether you consider them to be trustworthy.
One of my concerns was the security of my information on Facebook and I am happy to see that this is being taken relatively seriously by Facebook. When I chatted to the journalist from The Times earlier today I told her that Facebook users need to be careful about storing their credit card details on Facebook because is that information is not being secured then it can only go badly. Here is what Facebook is doing to secure your information:
Facebook takes appropriate precautions to protect our users’ information. Your account information is located on a secured server behind a firewall. When you enter sensitive information (such as credit card number or your password), we encrypt that information using secure socket layer technology (SSL). (To learn more about SSL, go to http://en.wikipedia.org/wiki/Secure_Sockets_Layer). Because email and instant messaging are not recognized as secure communications, we request that you not send private information to us by email or instant messaging services. If you have any questions about the security of Facebook Web Site, please contact us at firstname.lastname@example.org.