This is kind of a "for your own information/good" post.
There's a website called Spokeo, which I've spent the last hour or so on. If you enter just a little bit of information, a name, a phone number, whatever, you can find virtually anybody. This isn't really new for the Internet, there's all kinds of virtual phonebooks and whatnot. This site also gives you financial information and stuff like that if you pay $3 or so a month. The amount of information this website can pull for you about anyone is scary.
You can also run usernames through Spokeo. I entered the usernames of some of the staff members here and was able to pull up all kinds of accounts elsewhere - Twitter, Youtube, Tumblr, some Facebook information and so on.
There's a lot of information available on the Internet. Be VERY careful what info you give about yourself.