Do you want to learn more about someone?
There's lots of reasons someone might want to dig up dirt on someone. Maybe you're going on a blind date, need to rent out a room, or are hiring someone new to your small business.
Facebook and Google are a good start. I've warned you many times that all that fun stuff you're putting up on Facebook is letting out in public information that perhaps should remain private. In fact, you've probably used Facebook yourself to get a little bit of information on a new friend, acquaintance or prospective business partner.
But if you really want to learn about someone, there are specialized sites that go even farther and can dig up more dirt than what's posted socially.