I think Uber in the USA makes perfectly sense. Taxi service in most cities the US is horrible. I lived in San Francisco for six months and I have never seen such an unreliable, disorganized and mismanaged taxi service ever. Even in Kuala Lumpur or Saigon the service was better and more reliable.
In Germany the taxi service is well regulated and in the upper most cases very efficient. With the introduction of the very very good MyTaxi App it even entered the 21st century.
I addition you as a guest have certain rights when using a licensed taxi and you are insured when on board a taxi. With Uber it is just between you and the driver and god knows what happens if you get hurt in an accident.
To answer LR2013 question. If you are looking for a service you can order via an app take a look at the mytaxi app which is available for iOS and Android.