All this hatred against Uber is getting mighty suspicious! What is up with that? A taxi is a just a taxi after all.
Taking an unlicensed taxi simply means getting into a car with a total stranger. Most of the drivers are probably OK, and most of them probably drive reasonably OK cars; but you don't know that. You could be unfortunate and get the serial rapist, the drunk or the guy who drives something that is falling apart, although it looks OK on the outside.