haha. You see this happening at parties all the time. In fact, just like you said, the crowd usually picks on the one they already know to be a sucker for such challenges in the first place. And have a mighty laugh watching them go down. People who act upon the whim of others usually have issues and don't have any self integrity. They're always about proving themselves, even amongst a group of complete strangers.
Somehow, they just aren't pleased with themselves the way they are, love getting baited, and are always up for a (usually stupid) challenge.