I'd suggest delegated Gmail accounts: http://gmailblog.blogspot.com/2010/12/email-delegation-grant... used as contact emails for social networks.

I set up a delegated Gmail account for my son so that I can monitor and rescue the account. He uses Steam for online gaming (mostly gmod), and Facebook.

My daughter's iPhone is set up with my Apple ID, but her Gmail address is used for iMessage, Facetime, etc. Aside from the ability to use 'Find my iPhone' to locate her if necessary, I can also lock the iPhone remotely when I get a RenWeb alert that she didn't turn in her homework!