This isn't the first time AT&T has tried to get unlimited data customers to shift to its tiered data plans, . Prior to then, unlimited data was the norm for iPhone customers; upon tweaking its plan, AT&T also introduced the much-awaited ability to tether the iPhone's 3G connection to a laptop--but only for users of its tiered plans.

According to AT&T, the decision to throttle the heaviest data users is part of a plan to combat "a serious wireless spectrum crunch." Data throttling is only one part of the moves AT&T says it is making, with the company also investing money in building our its wireless network as well as trying to "acquire additional network capacity."

If you took that as a not-so-veiled reference to , well, AT&T's not exactly being shy about trying to drive the point home. The company concludes its announcement by saying that "Nothing short of completing the T-Mobile merger will provide additional spectrum capacity to address these near term challenges." It's a jab that's clearly intended to provide ammunition to help push the proposed merger .