With a few million people playing and actively trying to exploit your game, some issue are going to crop up. And Modern Warfare 2 has had some issues. But Infinity Ward is tackling them, including that recent infinite ammo thing.
IW's Robert Bowling updated the Modern Warfare 2 masses on the developer's current plans to fix some nagging problems. He writes, "Update in Test now: 1887s Balanced. Public "private" Match fix. Infinite Ammo fix. Prestige Hack on PS3 fix. Texture Hack on PC fix."
Looks like we can expect few double shotgun wielders in our future and less in the way of grenade spam. When all those updates will go live and onto your platform of choice isn't always Infinity Ward's call. But keep an eye peeled! I mean, stay frosty!