To clear up what was stated before, all you have to do is beat (win a match against) the person to claim the bounty. But it needs to be the first match after the bounty was placed.
yeah pretty much to beat the dead horse here, you have to find someone on the bounty list, then if u see their bounty hadn't been claimed.. hunt that bitch down like a rare animal.. and beat that fucker up easy version of it all >.>