Many of these free services - Facebook, GMail, etc, ask for additional personal information to help validate your identity. It seems counter-intuitive. If some of these sites can be hacked, do I want them to store additional information about me?
Most web site registration requests require a valid email address and the member's name. Anything beyond that is intrusive for a simple web site "registration" membership just to play a game or view and send email.
There are some other aspects to web site membership you should consider before offering any other information regarding your identity. Some of these would be relative to the "purpose" behind your registration, and what type of web site.
For example, you decide to perform your banking online. Your bank's web site is going to require much more personal information than just an email address and your name. In that example, you can see the need for providing such information. Before you do however, you should make certain the web site has protective features available, starting with the web site protocol itself.
When registering at a web site that requires personal information, look in the address bar of your browser. Make sure the web site address line starts with "HTTPS://".
Never use the same password at every site. If that site should be compromised, your account information could be readily available to the hacker.
You can have different passwords for different accounts. One way to keep track of this is to have an address book—the actual paper kind that you write in with a pen—stored near the computer (but not at it, or at least, out of sight from it). Such books are a great place to keep mnemonics and tips to help you answer password recovery questions for web sites. Keep in mind, though, that you should not write the actual answers to the questions in there, just something that helps you remember your answer.
If it is too much of a hassle to use a different password for every site, then use passwords for different types of sites, e.g. use a very strong password for financial sites, another strong password for email accounts, and an easier password for general site accounts.