If you're a smartphone user, and your network is AT&T (NYSE:T), prepare to pay up.

Ma Bell will be charging you a mandatory $30 fee for data usage if you're using any smartphone on its network, not just the iPhone. Want a new BlackBerry? That'll be thirty bucks a month, pal.

But really, this is an iPhone tax. A research report released in June by mobile advertising network AdMob says that Apple (NASDAQ:AAPL) devices account for 47% of the world's smartphone traffic.

Nokia (NYSE:NOK), the world's leader in terms of smartphone market share, was second at 33%. Research In Motion (NASDAQ:RIMM) placed third at 7%. Taiwan's HTC was fourth at 6%, and Palm (NASDAQ:PALM) trailed everyone with a 2% share.

For its part, AT&T said in a statement that it was serving customers with its pricing policy:

Smartphone users tend to consume a higher amount of data services, like advanced e-mail, mobile Web, applications and more. Being able to take full advantage of these features without having to worry about a fluctuating or unusually high bill generally leads to greater customer satisfaction, so effective Sept. 6, smartphone customers will need to subscribe to a data plan, as the vast majority of customers already do.

Balderdash.

The key portion of that statement is "higher amount of data services." Apple's iPhone users place a great strain on AT&T's network via data requests. Requiring a flat data subscription should reduce risk and increase predictability as Ma Bell earns a few dollars more.

To be fair, AT&T isn't requiring longtime smartphone customers who don't have a data plan to transition to one, unless they upgrade their equipment or calling plan, trade magazine InformationWeek reports.

How about we confine this to iPhone users instead? The iPhone is what it is because of its App Store, and applications consume bandwidth. In this case, unprecedented amounts of bandwidth -- more than 47% of the world's traffic for a smartphone supplier that held 13% of the market in the second quarter, according to Gartner.

By requiring data subscriptions from all its customers, AT&T is asking others to subsidize its iPhoners. How is that fair? This is one time you don't want to be politically correct, sirs.

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Fool contributor Tim Beyers had stock and options positions in Apple and a stock position in Nokia at the time of publication. Check out Tim's portfolio holdings and Foolish writings, or connect with him on Twitter as @milehighfool. The Motley Fool is also on Twitter as @TheMotleyFool. The Fool's disclosure policy is too tired to speak. (Yawwwwwnnnnnn.)