Gaikai is a scary concept. If they virtualize PS4 and could deliver a reasonable experience, it means I can continue playing not just on Vita but on Android and PC/Mac web browsers too. I can practically game anywhere. Would love an iOS client subscription model, like Music Unlimited.
For marketers, they can embed the game, or even replay saved games in reviews. For users, they can pick up their game instantly, right from the reviews say during DLC promotion. There are lots of opportunities extending BR and B&M shopping experiences too. Hope to see spectating (live or saved games) on the new Home.
I see huge challenges (some may be very difficult or insurmountable) and opportunities at the same time.