People talking about the dangers of completely unregulated cabs are missing the point. Unregulated cabs that you hail randomly on the street are dangerous because you have no way to verify that the cab is actually from the company it claims to be, and no way to punish the driver if he lies to you (or worse). You are completely at the mercy of the driver.

Uber is completely different from randomly hailing a cab on the street, because you can verify that the cab is from Uber and you can punish bad drivers with bad ratings. If you have a bad experience in an Uber cab, it reflects badly on Uber's brand, so Uber has a strong incentive to punish bad drivers. That's why services like Uber don't need the same regulation that regular cabs do.