How does Facebook manage to suggest new friends who are people you ACTUALLY know?

[v]

I find this a little intimidating- Facebook has a few times now suggested that I add certain people as friends. And this could be distant relatives, or old friends. Sometimes even people you forgot existed.
The thing is, I never gave out my last name, or any other personal details for that matter. Are they searching people through my email contacts list or something??

[Andrew]

i think they use your email and contacts from there, or it could be a friend of your own friend.

[Mike H.]

they are suggesting people that are probably friends with some of your friends.

[Jason Karpinski]

It's magic!! Could be email, could be just algorithms that look for similarities, for example people that went to the same school or live in the same city or state or have one of the previous and are mutual friends with somebody you know. It is creepy though. You'd freak out if you knew how much google knows about you.

[useyour_tool]

The internet has been watching you for years...

[Ryan Bezdicek]

They mainly use friends of friends. For instance, if friend A and friend B are both friends with C, then they will suggest you be friends with friend C as well. Facebook is also notorious for data mining, they keep any bit of information you give them and use it for advertising and suggestions like you are asking about.

[Chris]

it takes your friends and suggests people that are friends of your friends and have similair areas, schools, etc..