17 million of Xbox Live's 20 million active users have downloaded content through the online service, according to statistics released by Microsoft this week.
Although "content" isn't clarified, and includes videos and other non-game releases, the stat still gives an indication of the growing significance of downloadable items.
"Xbox Live data is kind of this untold phenomenon," Microsoft's Aaron Greenberg told Gamasutra in an interview hosting the data.
He added that paid downloads were up 73 per cent across the 12 months to the start of July, and said that "significantly outpaces what we saw in growth for console sales or software sales".
Microsoft has made a big play for downloadable exclusives as Xbox Live has grown, waving its chequebook around to secure downloadable Grand Theft Auto IV episodes and first dibs on Fallout 3 DLC.
At E3 it announced that the first two Modern Warfare 2 map packs would be timed exclusives on its system. It has also secured the Beatles song "All You Need Is Love" as exclusive Beatles: Rock Band DLC, with all proceeds going to charity.
Sony's competing PlayStation Network service for PS3 and PSP has 25 million registered users, the platform holder has said, and enjoys downloadable success of its own, including seven million downloads for PlayStation Home.