Legislation is usually not the problem. The contract that you sign when registering at a site is. You have to read it carefully because it usually starts out with something that sounds very good but you will always find some small exception that is explained just at the end of the TOS that in short nullifies all the good things said in the beginning. In most of the agreements you are bound by the terms while they reserve themselves the right to change the contents without having to inform you of the change (just as an example I found this at the end of Google's TOS "By accessing and using Google Services, you agree to be bound by the terms and provisions of the TOS // which may be updated by us from time to time without notice to you"). You will find similar content in all TOS's.