Things to keep in mind when using social networking websites.
1. Posts are not private. Even if you restrict access to your profile, it's always possible for information to be shared with others.
2. Posts are not anonymous. Clues in your profile can help to identify you. You can even be found through your computer's IP address.
3. Posts are not temporary. You can delete or remove information from a profile, but it still exists on other computers and in the files of companies that archive websites.
4. Posts are subject to the rules of online communities. Communities usually prohibit posting harmful content, and laws enforced offline can be enforced online, too.
Taken from "Let's Face It', a guide to social networking sites by the University of South Carolina.