Why does facebook suggest random friends, with whom you have no mutual friends?

[IdrisTheDragon]

I can understand it suggesting people with who I have mutual friends. But some of the suggestions aren't people I know and don't seem to be people my friends know either.

right my boyfriends ex came up on people you may know we have no friends in common not even my boyfriend and her why is she popping up on my facebook should i be worried?

I was trying to figure this out. In a recent case it was someone followed by a mutual friend.