AT&T today announced that it plans to throttle back the speeds available to wireless data customers who fall in the top 5% of data users. The company explained in a press release, "Starting October 1, smartphone customers with unlimited data plans may experience reduced speeds once their usage in a billing cycle reaches the level that puts them among the top 5% of heaviest data users. These customers can still use unlimited data and their speeds will be restored with the start of the next billing cycle. Before you are affected, we will provide multiple notices, including a grace period." AT&T didn't define what the top 5% of users means and said the actual number varies from month to month. AT&T noted that streaming video and music all day over the cellular network, as well as uploading HD video and playing multiplayer games is what typically adds up data usage the fastest. This change will not apply to customers with tiered data plans. AT&T says that the vast majority of its customers will not be effected by this change.