Newbies are also faced with a lot of un-learning to do. I tried playing a couple nights ago, and I couldn't hit for shit. Why?
L4D.
L4D will polish your reaction time, since a split second is the difference between winning and being treated like a Blooming Onion, but there is almost no accuracy component in L4D. You hold the button down whenever a zombie is near the middle of your screen. I was having no problem seeing people, but I was firing before I found the correct hitbox. Also, jump exploits, which we already discussed.
When people come in from games like L4D, they will not be used to the pass/fail nature of Goldeneye damage math. For myself, if I stick around for a day or two, I re-arrange my priorities and then it goes to MWtGG and I'm back in business, but players who don't understand why they're a living lamer spree will keep screwing up, even if they think they are aiming for the head like they're supposed to, and will become pissed when they see themselves as trying their best and still being torn apart by the top dogs.
I know because that night, discounting the jumphax incidents, I thought I was aiming for the head but then I started mentally screenshotting myself and realizing that I was still in L4D mode. Once I realized that I started hearing things like "IS EVERYTHING YOU DO A HEADSHOT?" again.