Rumors swirled Tuesday that Sprint Nextel would follow its competitors' lead on unlimited 3G data plans with cell data modems and cap monthly usage at 5 GB of combined upstream and downstream data. The company didn't respond to my request for comment on information discussed at the Sprint Users forum, which was based on an alleged leaked internal memo. (The forum has no relationship with Sprint.)

In a recent interview, a Sprint executive told me that their mobile broadband service was truly unlimited, save for abusive activities that degraded the network, such as operating a server over the connection or running continuous downloads at full speed for periods of time. It's not surprising that Sprint would downgrade unlimited to 5 GB, given that their two leading competitors haven't found it necessary to offer an uncapped service. If Sprint actually implements this cap on usage,it would almost certainly apply only to new contracts.

AT&T and Verizon both limit their customers who have what I call "unmetered" plans (there's no per-byte charge, just a cap) to 5 GB of bidirectional usage. 5 GB per month amounts to about half an hour a day of use at an average rate claimed by the three carriers. All three carriers offer unmetered service at $60 per month with a two-year contract, and $80 to $90 per month with no contract term.

AT&T says it takes measures when you cross 5 GB, including charging you extra, but isn't explicit about what it will do. Verizon has a clear policy: after 5 GB, you are charged 49 cents per megabyte ($490 per GB!) above that. Verizon said that customers with contracts underway could have their service throttled to 200 Kbps if they exceed 5 GB; new contracts get the overage charges. Verizon also said that their VZW Access program reports exact usage, and that they send email and text messages to notify you long before you cross the 5 GB threshold.

Verizon Wireless used to advertise their BroadbandAccess EVDO service as "unlimited," but after an investigation last year by the New York Attorney General's Office, the company agreed to drop the term, refund fees to subscribers, and paid a small amount to the state. Verizon now has the best and most complete disclosure of its broadband usage policies, including a long chart that describes approximate sizes of various items you might retrieve or send over the Internet.

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