I do realise it's possible to kill someone who's camping.
http://www.youtube.com/watch?v=05jtR9fZAnQ
Now if one guy had thrown a grenade or flashbang (Assuming the vid was based on CoD), Freddie would have died.
So yes, lots of people who get killed by campers deserve to get killed. But I just find it annoying sometimes, especially when it's your teammates getting raped by the guy with the M82.
A prime example from my experience would be COD:BO, on the map Villa. There's an upstairs window overlooking a courtyard and street area. There's almost always someone camping there and shooting up the other team.
Normally that's fine, they're crap. But sometimes you'll find one who's planned it out, or a pair with a good strategy, and they'll throw back your grenades and mow down your teammates and take a fair few people with them before they go down.
But hey, it's a legit strategy right? I've even done that a few times myself. But I've always made a point of jumping down and joining everyone else back on ground level after a minute or so, because I enjoy running around with my machine pistols more than camping.