[funnyman]

In my years contracting at the world's largest tech companies, I can tell you this: even the biggest three-letter-named companies in the world don't have their shit together. And despite what their TOS says, and despite their best intentions, data leaks out, be it by accident, intrusion, etc. So the only good policy is this: do not trust ANY entity with your personal data unless it's data you wouldn't mind seeing printed on the front page of the Wall Street Journal.

WRT having already posted your info on sites: consider conducting a formal disinformation campaign. Enter a birthday, but the wrong one. List the wrong college and high school. Do that on a couple sites. Upload random pics of people from the internet. Create a homepage somewhere, link to it in your social networking profiles, and then track who goes to that web page. Examine the web logs; you may be surprised where your visitors come from. Basically, create your own personal honeypot. You get the idea.