For better or worse, premium downloadable content will continue to be a fact of life for Call of Duty fans. Activision announced today that they've sold 20 million map packs for the franchise.

Activision unfortunately didn't provide a breakdown of those stats so it's not clear which map packs sold the most. It seems as though DLC sales have been steadily increasing over time, though. The first map pack for Call of Duty 4 sold a million units in nine days, the first pack for World at War sold a million in two days, and the Modern Warfare 2 Stimulus Package accomplished the same feat in one day.

It would've also been nice to see the sales broken down by platforms. The Modern Warfare 2 map packs were timed exclusives for the Xbox 360 and a similar agreement is in place for the next three years. I'm curious whether the move is actually paying dividends.