A person who you will think is your friend, only to find out later that this person spreads rumors and lies about you to your other friends.
A roommate who fronts a nice demenor, only because the rent is cheap. All the while attempting to sabbotage your personal relationships for his own gain.
John: Wally, Sarah just told me what you said.
Wally: I don't know what your talking about.
John: Dude you suck, she just told me that you said that I cheated on her and had girls stay at the house.
Wally: I don't want to talk about this right now.
John: Dude you know you have a crush on my girlfriend, and your just trying to sabbotage that because you think she would date your wierd ass.....Fucking backstabber!
Introducing one friend to another, only find out that the two friends enjoy eachothers company more so than that of the original Introducer. Thus leaving the original friend of both, friendless.
John: hey Jake what are you up too?
Jake: oh just hanging out at my house, playing video games with Wally.
John: Why didn't you call man? You know I wanted to hang out tonight.
Jake: Well Wally was already here when I got home.
John: Wally is such a friend thief.