I can kind of see where they're coming from there; it had to be a Valve game and that's the most recent one. I imagine they could offer a small amount of credit (if that's even technically possible), but I imagine giving away a full game from another publisher would create a bit of a problem.
Agreed w/ all of that, GPW.
Now that I really think about it, Valve was damned if they do or damned if they don't here. They couldn't win on this one - people were still gonna bitch and moan, regardless - and rightfully so, pretty much. I'd be bullshit if I got slapped w/ a VAC wrongfully and lost access to my game, too.
I suggested Valve could've given credit to say their next full-priced game for those 12,000 or so false-banned gamers - maybe it'd be...HL3? L4D3? Portal 2? I dunno - but, maybe some would've complained they couldn't get a current game like L4D2 (if they didn't already have that already)?
Hell, I dunno... *shrug* But, yeah - Valve put themselves in a lose-lose situation (dilemma) here.
EDIT:
You know what would've been worse? If Valve offered up FREE copies of Alien Swarm to those MW2 false-bans.