The reason they "get away with it" is because those little car alternator wind turbines are incredibly popular with hobbyists. Hobbyists don't necessarily need a "real" wind turbine - they just want one that goes around and puts out a few amps now and then.
There has been some off-gridders I know who have bought them that are happy with them. And others that complain that they don't produce any power. I think the difference is that the ones that are happy with them have decent wind sites and have them on a tower that is in a decent location. Most of these little things are put on a piece of pipe on the end of the house, or sometimes on the roof. They aren't going to produce anything there, just like any other wind turbine won't. But put it on a 90 foot tower, like I know one guy that has one has, and the turbine actually works.
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Chris