I wrote a long post about this, but in short:
Yes, lag comp exists to the non-believers. I called Activision they admited to it. Call for yourself.
Long time COD fanboy.
Defended Activision/COD through the BF3 debates.
Preordered past 3 games.
Didn't care about nukes, perks, QSing, etc etc etc. Just played the game because I had fun.
Have gotten 5+ hitmarkers in HCTDM and die from a turn around single shot.
Call it what you like.
Call me a bad player.
Call me anything, I care not, my friends.
I'm done with COD because of this.
It has changed since BlackOps/MW2. My k/d was over 2.1 in mw2 and 1.98 in BO, but MW3? 0.9. I've been gaming since the 80's. I'm not a bad player, this is a bad game.