I have employees and contractors working for me and we have very strict rules on what contractors can do, how you interact with them and when they might be considered employees. The company I work for wants to stay clearly on the legal side of contractor law.

If it is proved illegal then Uber will owe these people back pay and possibly back benefits which might collapse Uber and that is fine. If you want to run that close to the edge of the law then you have to accept the risk. But let these laws and judgments catch up with the new economy/technology.