Verizon, the parent of TechCrunch’s parent AOL, is being accused of violating net neutrality principles by excluding its own mobile video streaming service, go90, from data charges — thereby creating an unequal playing field.

On Friday it emerged (via The Verge) that Verizon would not be charging its own customers for the data they consume over go90 . An end of January update to the go90 Android app (v1.4.0) notes the service can now be used over LTE without it counting against Verizon customers’ data plans:

If you’re a Verizon wireless post-paid customer, stream go90 videos over LTE without using up your data.

Verizon has long since stopped offering new customers unlimited data plans, and instead sells a selection of tiered plans starting at $30 per month for 1GB rising to $100 for 18GB (you also need to pay $20 per month per smartphone line, plus taxes). So its data costs can get pretty expensive, especially if you’re in the habit of watching video on the go. Which makes a zero-rated video service sound pretty appealing.

Yet such a freebie has the obvious knock-on effect of penalizing other video services that do cost data to consume (and thereby eat into users’ data allowances). Hence critics calling foul over the move — which looks like an attempt to circumvent US net neutrality laws, passed by the FCC a year ago.

Verizon’s argument for the legality of the service is that go90 is open to other content providers via its sponsored data program, FreeBee Data 360, which lets content providers pay for customers’ data costs. A Verizon spokesperson told Re/code: “FreeBee Data 360 is an open, non-exclusive service available to other content providers on a non-discriminatory basis. Any interested content provider can use FreeBee Data 360 to expand their audiences by giving consumers the opportunity to enjoy their content without incurring data charges.”

However, as Re/code notes, Verizon is pulling the strings here. So rivals merely wanting to compete on an equal footing with Verizon’s free service would still have to pour data costs into Verizon’s coffers just to do so. Which again skews the competitive landscape.

Carrier AT&T has also said it is planning to launch a mobile video service involved sponsored data — so as industry watchers have noted the Verizon move is something of a test bed to see how the FCC responds.

The body has already said it is looking at zero rating to determine whether the practice violates its general conduct statement. In the meantime, carriers are clearly seeing how far they can push things…