You guys need to realize that CoD is all about the multiplayer. Who cares if the campaign is short? I haven't even played the single player yet. All that matters to me is that I was playing CoD4 regularly up until about 2 days ago. I've been loving every minute of MW2, which is basically CoD4 but with way more ability to customize buildouts, and with a new multiplayer co-op component. I have absolutely no reservation with paying 50 bucks for that. As far as the message that we're sending to the gaming industry, it seems to be: if you make an awesome game, with multiplayer that offers hundreds of hours of replay value, a lot of people will buy it. I'm okay with that.
BTW, I game on PC, PS3, and 360. I bought MW2 on 360 because I prefer the ease of use for Xbox Live. I know that all the PC gamers will look down their nose at me because of this, but frankly I don't care. Have fun boycotting every game that doesn't give you exactly what you want, I guess.