AT&T Inc. (NYSE: T) is taking a lot of flack recently for the idea that it could possibly move to a more tiered pricing system to discourage excessive wireless data usage by subscribers on the iPhone and other smartphones. (See AT&T Mobile Boss: NYC & San Fran Are 'Underperforming'.)

At a UBS AG conference in New York last Wednesday, Ralph de la Vega, head of AT&T's Mobility unit, said the operator is considering ways to get consumers to reduce their data usage. This has started major hand-wringing on wireless blogs with the Fake Steve blog even suggesting that users hold a so-called data riot in a bid "to teach AT&T a lesson."

AT&T is by no means the only U.S. carrier to consider other ways of pricing wireless data, however.

AT&T's major rival, Verizon Wireless , said as far back as April 2008 that unlimited data pricing plans were unsustainable in the long-term. Talking to Unstrung at that year's spring CTIA show, CTO Tony Melone was already talking about a more metered approach to wireless data.

"You will not see unlimited flat-rate pricing on data, in my opinion, in the future," Melone said in 2008. (See Tony Melone, CTO, Verizon Wireless.)

"There is a limit to how much people can talk in a given month, yet the industry took 25 years to sort of get to... unlimited voice," Melone said. "With data, where's virtually no limit on... consumption; the industry went right out of the gate with unlimited, which is kind of backwards in my opinion."

You can click on the video below to watch all of Melone's comments:

AT&T and Verizon, as well as rivals like Sprint Nextel Corp. (NYSE: S), however, are still pushing "unlimited" data plans today. As the reaction to AT&T's de la Vega's comments show, a move away from unlimited pricing seems like it would be unpopular with wireless subscribers.

Of course, unlimited doesn't actually always mean unlimited in the wireless world. For instance, Verizon's $29.99 unlimited plan for the new Droid phone caps data usage at 5 gigabytes a month.

The traffic and charging issues are unlikely to ease up for carriers anytime soon. With more and more netbooks and laptops going mobile there are an increasing number of devices on networks that can pull down large amounts of data.

— Dan Jones, Site Editor, Unstrung