I've seen a lot of people with "troll" on their name, but this like you said does not mean he is a filthy troller, sometimes people are amazingly good at the game no matter what their name is. I never judge people by their name until i've played with them. If they are a troll then I usually come up with a better name suited for them and then send it through a message. Just a reccomendation message i say. Only as usual they don't respond, quite funny sometimes.
Watch Vanossgaming. His zombie videos are hysterical...I dont have a problem with trollers. You play the way you want and they play the way they want, simple. You can still carry the game to a high round or pull a joke or two on them and roll(troll) with it.
The purpose is to use other people's negative emotions for their pleasure and entertainment.
Surprisingly enough, not all the time, no matter what map I'm on there always seems to be somebody who thinks its funny to mess people around. Especially on buried, this freak that I met thought that he could get the time bomb, so he did and then put it down on round 3, then when we all pack-a-punched and got RGM2's he just randomly flicked it and we lost everything, all we could hear after that was his squeaky laugh. One guy in the lobby hacked him off xbox live and rendered his IP address as blocked so he couldn't make another account. I was happy he wouldn't be doing that anymore but that was only 1 in thousands of dum, stupid and completely unwanted trolls.