An anonymous reader quotes a report from TmoNews: T-Mobile's new deprioritization threshold is 30GB of usage in a single billing cycle. While T-Mo didn't make an official announcement about the change, you can see in this cached page that the network management policy says 28GB: "Based on network statistics for the most recent quarter, customers who use more than 28GB of data during a billing cycle will have their data usage prioritized below other customers' data usage for the remainder of the billing cycle in times and at locations where there are competing customer demands for network resources." Navigating to the webpage today now says 30GB. What this change means is that if you use more than 30GB of data in one billing cycle, your data usage will be prioritized below others for the remainder of that billing cycle. The only time that you're likely to see the effects of that, though, is when you're at a location on the network that is congested, during which time you may see slower speeds. Once you move to a different location or the congestion goes down, your speeds will likely go back up. And once the new billing cycle rolls around, your usage will be reset.