A series of stories yesterday appeared that said T-Mobile used to allow 10 GB per month of unmetered data use: This is incorrect. In April, T-Mobile switched from the standard U.S. carrier model of charging overage fees of 5¢ to 20¢ per MB for data used above 5 GB on the higher of two metered plans (see "T-Mobile Offers Overage Compromise: Throttling," 27 April 2010). Instead, T-Mobile switched to what European carriers typically employ. After using 5 GB during a billing period, the data connection is throttled to about 64 Kbps. Some customers might like paying $50 to $200 per GB over 5 GB; others might like the soft landing.
Stories yesterday, such as this one from a site devoted to T-Mobile news (TmoNews), stated, "If you may recall, previously the data cap was 10GB/month." I checked with a T-Mobile spokesperson, who confirmed my recollection was correct. I have spoken about this with T-Mobile several times, too, since April, and the cap was always 5 GB.
What may have spurred the confusion is a document that talks about such throttling starting "October 16"; TmoNews has a photo of the internal document meant for T-Mobile sales agents.
This kind of throttling, by the way, won't be mandated nor disallowed by the FCC under new disclosure rules it's imposing on carriers, but it certainly fits within the framework the FCC has set. The FCC wants sticker shock banished, and will force carriers to provide notifications before a customer hits a point at which fees will be charged. Many carriers offer mandatory or optional methods to be notified (at no cost) of such limits. But not all do, and international roaming is especially egregious. It's also difficult to turn off service to prevent such overages from happening accidentally.
T-Mobile, by pursuing throttling, with no extra fees involved, ensures customers on the 5 GB plan never pay an extra cent; they just have to cope with lower bandwidth.