AT&T, the No.2 wireless carrier in the U.S. and smartphone leader, has introduced new smartphone data plans and is now the first major mobile phone company to stop offering a single monthly price for unlimited Internet access — now new smartphone customers are charged based on how much they really use their mobiles to access data, videos or music [DataPlus: $15/mo. for 200 MB of data or $25/mo. for 2 GB]. Existing customers can switch to the new pricing or keep their current all-you-can-eat 30$-service.

Why is AT&T doing this?

According Silicon Alley Insider for a bunch of reasons: But big picture, because the amount of money that wireless subscribers spend on mobile voice calling is shrinking. Meanwhile, data consumption is increasing, but data revenue is barely increasing at the rate that voice revenue is decreasing. AT&T says 65% of its smartphone customers use less than 200 MB a month, and 98% (!) use less than 2 GBs of wireless data a month. So signing up will be cheaper for the bigger part of new subscribers and AT&T needs to generate growth in its wireless business. With the limited airwave spectrum available for wireless broadband, a Nielsen analyst adds, it’s just a matter of time before other providers — including Verizon, Sprint and T-Mobile— switch to usage-based pricing.

What you can do with 200 MB or 2 GB, AT&T shows it in this chart:

Source: AT&T usage example