Federal Communications Commission Chairman Tom Wheeler is asking all mobile phone carriers to explain their throttling practices. He esp. targeted Verizon, which announced recently that it will throttle the top 5% of users when their network is overloaded.

VVerizon stated: “In short this practice has been widely accepted with little or no controversy.” Wheeler told reporters that “‘All the kids do it’” is not a reasonable defense of the practice.

“My concern in this instance—and it’s not just with Verizon, by the way, we’ve written to all the carriers—is that it is moving from a technology and engineering issue to the business issues ... such as choosing between different subscribers based on your economic relationship with them,” Wheeler said.

He did not release the letters to the other carriers. But this saga is far from over.