A closed beta would have been fine. There are a lot of people driving Telsas who do know more than a little about computer vision and robot localization. Telsas engineers and programmers probably know many of them, or at least know who they are. Give it to just them. They'll not only have a sense for the limitations, they know how to write a good bug report.
Not sure I agree. Traffic is a system of which cars are a part; the beta participants can be driving them but everyone else is then subjected to the same beta, whether they like it or not. The guy who got decapitated was speeding and watching Harry Potter. He plowed through a telephone pole a quarter mile after he turned his rig into a convertible. He wrote his own luck. But the semi he hit because the Tesla didn't "see" it? What if it was a girl in an Easter dress? The truck driver wasn't a willing part of Tesla's system. Neither are the rest of us. And I feel they should have done substantially more testing before rolling it out.
Once they're at the point they're even considering releasing the thing, it's already on the road anyway because they're testing it themselves. The difference between that and letting knowledgeable customers test it for them is just that they've conned some suckers into working for free.