According to a report at Eurogamer, the physical disks for Call of Duty: Modern Warfare 2 contain only 70MB of data on them. That tiny amount basically means the disks are physical DRM keys and nothing more.

Instead of the game, discs have just 72MB of data and the rest must be downloaded. The disc versions of the game appear to be functionally identical to digital copies. Instead of buying the license and downloading it, you purchase a disc that ships to you with a license key.