In part they already exist as a buyin product in the form of flipout mtt's on ftp, only different being its only a single round of the allins and then its an actual game to play.
Also full tournies exist on some sites, like intertops
and prob the other revo skins called kamikazi tournies. I know partypoker
has a hu game where its just an allin flip.
The flipout seems to have some popularity on ftp but i think its only going to be something that can exist where there is traffic to find the players who are willing to play them.........but the kamikazi style allin shootouts like these promo's would be pure gamble as a buyin so anyone looking for anything besides an absolute gamble I don't think would be bothered other than possible throwing in a buck here and there for pure gamble.