If you're reading this article, chances are good you have a page on Facebook, too. More than 150 million Americans already use the site, and the number grows daily because Facebook makes it so easy to keep up with friends, family, and colleagues, discover great content, connect to causes, share photos, drum up business, and learn about fun events.To deliver this service, Facebook and other social networks collect enormous amounts of highly sensitive information—and distribute it more quickly and widely than traditional consumer data-gathering firms ever could. That’s great when it helps you find old classmates or see ads for things you actually want to buy. But how much information is really being collected about you? How is it being used? And could it fall into the wrong hands?