I think Santos might be right. A couple of years ago we ran into some friends that were using a local cab driver. After a couple of drinks they wanted to pay him and send him along to join us. The cabbie threatened them and us with the Politur and all sorts of violence if they chose to ride with us.
They never had a agreement with him but he saw us as taking his fare. I know all the local cab drivers in the PC area are unionized and they use boarder line mafia tactics so I don't know how a Uber operation would work here.
I'm sure they would be beaten at best and killed at worst. Our friends ended up having to give the cab driver $50 USD just so he would leave them alone. I guess another word for it is extortion.
I used Uber from Santo Domingo to the Hotel Riu Palace in Bavaro. The driver informed me that I would not be able to use the service for the return, but he provided me his phone number to contact him, and he'd offer me the same rate when I wanted to return ten days later. All worked out well. Not a problem.