Cheating, hacking, lag switches, glitches, host problems, connection issues, terrible map packs, auto-aimers, modded contollers, just to name a few. Infinity Ward didn't fix glitches, they had all kinds of connection problems for not having a dedicated server. Their offerings in the map packs were absolutely garbage. And once you bought the map packs those were the only maps you ever played. World at War was a better game than Modern Warfare 2 and everyone complained about how bad that game was and couldn't wait until MW2 came out.
