searching for people on the internet

Suppose you want information about someone. You might want to find a lost relative or friend, a guy who owes you money, do a background check on a potential business partner etc. Where can you turn?
Mashable.com, a site that describes itself as providing social networking news tested 6 sites that try to help you find people. Here were some of their findings and my own ideas:
PeekYou-their information is not up to date
Wink: I actually found this site myself through Google. Mashable likes the site. Its a meta people search engine. When I tried my name it linked me to Intelisearch. But I had already searched them (and decided not to pay them $2.99 to get more information on myself). One thing I give wink credit for is it got my dads name right.
Spock- they are in beta mode. I tried my name but didn't come up.
ZoomInfo-business people name search. Now this one may be a real find! I once worked as a salesman selling shopping and garment bags to retail chains. I used to call the buyer for the company and try to establish a connection and pitch my product. Some buyers will talk to you on the phone. Others are too busy and just want you to send them a package with information and a sample. But sometimes its hard just figuring out who the buyer is. This was my case with Victorias Secrets. They were very secretive about who their buyer was. It was like "if you know your party's extension enter it now and if you don't know your party's extension please hang up." ZoomInfo has a section called ZoomExec and ZoomPowerSell. Through them I might have been able to get my answer. I think ZoomInfo should be looked at more carefully and considered as a reference resource to be used by librarians. Too bad its not free.