If you're a T-Mobile customer and a heavy data user, listen up--T-Mobile will begin throttling your data usage after you hit the 5GB limit, starting October 16.
The unofficial T-Mobile blog, TmoNews, reports that T-Mobile will begin reducing data speeds after a customer uses 5GB of data in one billing cycle. When customers hit the 5GB "cap," they'll receive a free text message stating that their data speeds will be reduced. It's not clear by how much data speeds will be reduced, but T-Mobile says that the type of device will determine the speeds.
The "cap" will only last for one billing cycle--once the billing cycle is up, the customer's data speeds will be returned to normal (again, up to 5GB). I call this a "cap" because it's not really a data cap--after all, T-Mobile is throttling your data, not cutting it off. While this is nicer than having to deal with overage charges (the 5GB data plan is, essentially, an unlimited plan), T-Mobile's "cap" used to be 10GB.
T-Mobile says that the new "cap" will affect less than one percent of its customer database, which sounds about right. To give you a handle on how much 5GB of data really is, T-Mobile gives the example of Yahoo.com page visits. 5GB of data will get you approximately 125,000 visits--a pretty decent figure. Another figure for reference--about 1MB of data will let you send about 100 emails (without attachments). There are 1024MB in 1GB, so 5GB of data will let you send at least 500,000 emails.
Of course, a lot of people take the "bigger is better" approach to mobile data plans, and will feel as though they are being deeply affected by this change--even if they aren't. (For example, the newest iPod Classic peddles itself as being able to hold up to 40,000 songs, even though most people will never have 40,000 songs.)
That said, if you are worried this change may affect you, you can always monitor your T-Mobile data usage online: just go to my.t-mobile.com and click on the "monitor use" tab.