T-Mobile USA's recently instituted practice of downgrading video quality to 480p in order to reduce data usage now has a prominent critic: YouTube.

“Reducing data charges can be good for users, but it doesn’t justify throttling all video services, especially without explicit user consent,” a YouTube spokesperson said, according to a Wall Street Journal article today.

T-Mobile's "Binge On" program automatically reduces the quality of video while allowing many video services to stream without counting against customers’ high-speed data limits. Video services that cooperate with T-Mobile by meeting the company's "technical criteria" have their videos exempted from customers' data caps. Netflix, HBO, Hulu, and many others worked with T-Mobile to get the exemption.

YouTube, owned by Google, was notably absent from that list when T-Mobile announced Binge On last month. YouTube videos thus still count against data caps, but YouTube isn't exempt from the throttling. Binge On is enabled by default, reducing quality for all video services, unless customers shut it off by going into their account settings at my.t-mobile.com.

YouTube's statement did not mention T-Mobile specifically, but YouTube confirmed to Ars that it is having conversations with T-Mobile about Binge On.

Federal Communications Commission Chairman Tom Wheeler initially called Binge On "pro-competition" and "pro-innovation." But the FCC last week asked T-Mobile to meet with commission staff as part of a net neutrality inquiry. The FCC also contacted Comcast and AT&T about their own implementations of data cap exemptions.

YouTube has apparently not made any filings with the FCC about Binge On.

According to the Journal, "T-Mobile declined to address YouTube’s complaints. In a statement, the No. 3 US carrier by subscribers said its customers 'love having free streaming video that never hits their data bucket' and like 'both the quality of their video experience and the complete control they have.'"

UPDATE: A T-Mobile spokesperson declined to answer questions, but pointed to a tweet from CEO John Legere, which said that Binge On gives customers "streaming video w/o hitting their data bucket AND complete control to turn it on/off at will!"

T-Mobile's Binge On was also criticized today by the Internet Association, a group that includes Google, Netflix, Amazon, Facebook, and many other Web companies.

“T-Mobile’s new ‘streaming optimization’ program appears to involve throttling of all video traffic, across all data plans, regardless of network congestion," the group said in a statement that praised the FCC for looking into the program.

Binge On is enabled by default even for T-Mobile customers who pay extra for unlimited smartphone data. The main benefit of Binge On for unlimited data customers is the ability to stream video without it counting against their mobile hotspot usage—while smartphone data is unlimited, tethering data is not.

The Internet Association argued that T-Mobile shouldn't automatically opt customers and video services into the Binge On program.

"Reducing data charges for entire classes of applications can be legitimate and benefit consumers, so long as clear notice and choice is provided to service providers and consumers," the group said. "However, a reasonably designed zero-rating program does not include the throttling of traffic for services or consumers that do not participate."