I'm not sure about *all* of the United States, but it's legal in New York (City) and it's great! Usually, I can get an Uber ride way faster than a cab, it comes out a little bit cheaper, and you pay by credit card (already stored in the database and not at the point of transaction) without worrying that your card just got cloned.

Here too, people do a lot of underhanded things when it comes to cabs. For instance, you're waiting at a corner to hail a cab, so someone will flag the cab that's heading towards you in the middle of the street and steal your ride. With Uber, the car is designated for you, so there's no ride theft. :)

My city of Houston Texas has a population of more than 3 million people and is very spread out. We have lousy bus service and public transportation is a joke. (2 short rail lines) So the vast majority of citizens get from place to place in cars.

There are many taxi companies here, and they have tried desperately to stop Uber from entering the city. However, Uber has become more popular. The disadvatages are:  the question of insurance for passengers, the quality of training for the drivers, and the lack  vehicles to transport the handicapped. The advantages:  lower price , and the assurance that the car you call for is YOURS alone.

In my country it has forbidden. I think that is not the solution. I believe that it must be regulated correctly and pay taxes like similar services like taxis or bus and compete in the same conditions.

In Brazil Uber is in what we called a gray area of the law. Some cities had addopted it, but in full scale. 

Personally, I think it's a brilliant idea, and a very contemporary example of one of our age's biggest problems: technology that advances much faster than governments can adapt.

It, as well as a few other similar apps are legal here on the west coast. I believe some cities have tried to ban it, mostly for a lack of things like insurance (and other regulations that taxi companies must abide by).

Unfortunately in Los Angeles, taxis are not really able to compete. In fact, depending on how far you need to go, limousine service is cheaper (I use limos to go to LAX airport, because long term parking is more expensive). Public transportation isn't that good in a lot of places, but most people drive themselves so things like Uber work pretty well!