FPS's like COD and Halo are terrible for camping, which is why I don't play them and instead play arena FPS's, where you have a bigger chance of staying alive if you're running around, dodging off every possible object in your path. There's a mod on Unreal Tournament where everyone is alerted to your position if you stay within a small section of the map for so many seconds. It's not really needed on UT, but it's a good idea still, although I don't think it'd work so well on COD or Halo.
I don't mind camping/slow progression if the game is suited for it, like Battlefield or Arma, but on COD it's just boring, and even more boring when you die by a camper shooting an endless amount of grenades with a 20ft blast radius from his forehead in a window next to his spawn, with a radar as all seeing as God and a black hole he can pull infinite claymores out of. Actually, that just sounds like bad game design.. but meh, that's opinion, I don't like FPS's like COD or Halo, which seem to either encourage camping, or just leave it because it doesn't matter what they do, they still get teh monies.