After a week of accusations and F-bombs, we have a pretty good idea of what T-Mobile’s free streaming service is all about.

T-Mobile’s “Binge On,” which lets phone customers watch certain videos without using up their monthly data plan, didn’t seem like a big deal at first. But now the company is caught in a controversy over apparent lying, its CEO is dropping f-bombs and the long-simmering fight over net neutrality is heating up again.

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This assessment is consistent with what Barbara Van Schewick, a net neutrality authority at Stanford Law School, told Fortune last month in an interview about free data offers.

Van Schewick considers Binge On to be in a “grey area” when it comes to the FCC’s rules, but she also fears the program could serve as a Trojan Horse for other carriers that want to push the envelope even further.

These include Verizon, which announced a planned “sponsored data” program in December that would involve content companies paying to fall under a data-exemption umbrella. The company has been mum about details but, according to Van Schewick, such a pay-for-access scheme would fall afoul of the FCC’s general conduct rules.