This here ..is a mess of points(not a single one bullet), sorry:
Usability.
No discs to swap and such with cloud - Can be a hassle with traditional. Also disc based media can be scratched, worn, fail, etc... But then again, cloud based reliability is at the behest of whoever's serving it. What kinds of games could be more/less advanced based on the performance(bandwidth), and social(online) trade-offs?
Cost.
What types of games would cost how much to serve over a cloud? Would companies charge fairly, or the same as retail even when it should be cheaper? if subscription based will the costs eventually be more than if you just bought all the games you play traditionally? How does it compete with services like XBOX Live that serve to complement traditional games? Do you value a physical copy? If ad based, is that too intrusive?
I didn't exactly stick to a strict definition of "cloud" ... My thought got lost in a mix of the gametaps and steams and xbox live arcades and online card games and chat rooms and some concepts I've seen .......but anyway, those are my thoughts.
