I want the PC version. All of my IRL friends will also want the PC version. No one I know will want the PS3 version. So look at it this way:
I could either 1) buy the PC version straight up, or
2) buy the PS3 version, use the code, sell the PS3 disc back to Gamestop, someone else can buy the "used" PS3 version for less than the new version, Valve still gets all the money they normally would have gotten from a new PS3 version sale, and I have the PC version and someone else has the PS3 version, which is exactly what Valve intends to happen anyway, and is why they're doing the promotion. I really don't see how that's morally questionable.