Activision is looking to do something that so far only the PC gaming industry has been successful at: that of course is subscription-based gaming. Now there are some distinct differences between their subscription-based service and that of World of Warcraft, which serves as a good basis for comparison. If that seems confusing, just ignore the fact that CoD and WoW are on different platforms.
The release of Activision's 'Call of Duty Elite' service is scheduled to launch this fall and will probably coincide with the November 8th release of Call of Duty: Modern Warfare 3 since that is the game the Elite service is going to work with. Players are already used to shelling out $60 on a new title and the concept of DLC seems to be going over well so why would Activision try to milk the franchise even more with a subscription service? The short answer is, because they are Activision. Those of you who understand what I mean will be able to stop reading here.
For those who need more on the concept, including possible price-point, hit the break.