* There's an official definition for what a "fare" is, and cab drivers can't change it in the middle of a trip.
* Cab drivers lose their medallions if they drive people around in circles to rack up fares.
* Cab drivers lose their medallions if they randomly drop people off halfway to their destination.
* The insurance requirements for cab drivers are much more strict than for noncommercial drivers.
* Cab drivers are more stringently licensed than normal drivers; in fact, with "P2P car service", there's no incentive to be licensed at all. Reckless driving is a huge problem with urban cab drivers.
* Taxis themselves are inspected for safety, and cab companies risk their licensing by fielding cabs with bald tires and fucked up brakes.
There are two obvious reasons why you'd want to be careful about using the Internet to route around taxi regulation:
* There is no incentive whatsoever for "P2P car services" to follow safety, insurance, and fair business practice rules, because a bad actor can simply re-register their car with a new account.
* The P2P system cannibalizes the regulated taxi system, which offer far more consumer protections.
That's a start. I don't think it's crazy at all --- though again, I'm not arguing that this Internet service should be outlawed.