agreement before you sign up for anything.
In the USA, you automatically "own your own words" under law - UNLESS - you enter into an agreement to waive your rights.
Clicking that little check box that says "I have read and accept the terms and conditions..." is all it takes to irrevocably waive your ownership and control over anything you put up on a given website.
Despite the fact we're in a digital world, one bit of advice still holds: Know what you are getting into before you sign on the dotted line!
Unfortunately, it's almost impossible to know what you're agreeing to, since nearly every site has a "subject to change without notice" clause built in to their usage contract.
So I guess the answer ultimately depends on who you're dealing with. Just like everything else, come to think of it.