From what I've been told, Sprint and T-Mobile charge MVNOs (networks using their infrastructure) by the byte. Google can't offer unlimited data without running

From what I've been told, Sprint and T-Mobile charge MVNOs (networks using their infrastructure) by the byte. Google can't offer unlimited data without running their own network or taking big losses on customers that use a lot of data. There are no data caps on Google Fiber, so they seem to realize that caps aren't effective for managing congestion. But for now they have to play along with the big networks' models.