Google buys Valve: Valve likely continues making games the way they used to, Steam gets more games due to marketing deals, being essentially third party and the industry`s most popular source for downloading games. Google and Valve profit.

Valve stays alone: Valve likely continues making games the way they used to, Steam gets more games due to marketing deals, being essentially third party and the industry`s most popular source for downloading games. Has to deal with occasional uppity larger corporations, hostile takeovers and competition like Direct2Drive.

Valve gets bought by Microsoft: Microsoft uses leverage of digital distribution to smother competition, redirecting consumer attention to promote sales of their own games... Microsoft profits immensely since no exploding consoles are involved.

Valve gets bought by EA: See Microsoft, minus past console-related travesties and sudden intimate outbursts between Jerry Seinfeld and Bill Gates, the only positive of this situation.