well, yeah youre probably right, marketing could be more efficient, but youre example has a minor flaw i think, because if you consider that so and so many PC gamers also own a console, then its highly likely that this ad might also affect some people visiting that site... guess it always comes back to statistics huh?
While some dedicated PC gamers have consoles as well, I would assume it is a small percentage that play online FPS games on an Xbox 360. I mean, I could be wrong... but even if I am, wouldn't that still be pretty far down the totem pole of sites you target with that sort of thing? I haven't seen those ads on normal gaming sites nearly as much.
Maybe it is part of Microsoft's plan to get all PC gamers to switch over, I don't know, but when I see it on three or four dedicated PC gamer websites on the same day, such as Blue's News, it just seems a little off to me.
That's just one example in a sea of wasteful marketing though, at least in my opinion.