The informal look is still in "very early stages" but is also investigating complaints about limitations for what third-party companies can do using carriers' data networks, the rumor adds. Critics have often accused companies of blocking certain media download and VoIP apps not because of carriers' self-proclaimed bandwidth issues but to prevent legitimate competition from rival services. Still questionable but substantial allegations have charged AT&T with limiting SlingPlayer to Wi-Fi to help its own IPTV service.

Carriers themselves have long denied these claims, arguing that exclusivity deals lets them guarantee a lower price for a given phone and that they've been willing to remove barriers to certain kinds of apps when technology allows. AT&T, for example, told Electronista earlier this year that it will accept VoIP on 4G much more freely as the latency should be low enough to permit more natural conversations.

It's unknown how close the Deparment might be to launching a formal investigation.