Okay so is Steam enough of a money printer for Valve to say "well fuck you guys, we'll make our own credit card with hookers and bingo"? And hold out Half-Life 3 (only purchasable with the ValveCard) as a carrot?
I mean, if there's one company that I believe could pull that off is Valve. And maybe Amazon. Maybe the two together. It would be one hell of a JV for both parties.