People search engines border on creepiness
PCWorld.ca has a good article entitled People Search Engines: They Know Your Dark Secrets. . . And Tell Anyone. It talks about search engines meant to find information on people, such as www.pipl.com and http://www.spokeo.com/ .
They search various public sites to get the information, such as social networking sites, amazon wish lists, flickr, etc.
Put your own name in and see what comes up.
One issue is that the searches are imperfect. They of course pick up information about others with similar names, or amke certain assumptions. In my case, for example, it included as one of the several photos that purport to be me, a photograph of a fellow board member from a group photo I was in.
This also emphasizes that we all need to think about what we post online. The safest approach is to only post information that you would be glad to share with the world.