Interesting look at the effect from fan contact and interactions from The Economist. This could be in the context of fans-to-player/talent or fan to entertainers (mascots/dancer/performer). Many teams and leagues have offer some guidance on how to interact (or not to interact). Based on this it would seem short fist bumps are in vogue… if you venture out into the unwashed masses.
Also this older (and really funny) clip from the Harlem Globetrotters, which might be in the new style-book for how NOT to give a high five.