Steam vs Xbox Live

This came from an interview with Valve's Chet Faliszek on IGN:

"Another factor is that we update the PC side all the time, and the way Xbox Live works we can't do that. If you look at Team Fortress, we're updating that once every two weeks, and it's frustrating because we can't do that [on the 360]. We have a big update coming up on the 360 and we're going to keep updating the 360 version but they're not in step with the PC version."