COD has damage drop, usually to the order of 50-40, 40-30, 40-20, 35-25, etc.
All Sniper rifles and most LMG's have a flatline damage value in mw2 and BO
Not like in real life standing 30ft back would make a bit of difference
What I would LOVE to see is RISING damage for sniper rifles, example 40close-70far in cod and 50-70 in BC, would absolutely BREAK quickscoping, which relies on massive damage at close range with no time for opponents to shoot back. Now if you found a way to quickscope with those damage numbers you would only get hitmarkers unless you did it at a range, in which case QS'ing is inferior to standard firing.