IMHO anything that cost-effectively shifts the responsibility for the actual driving from "me" to "somebody else" is almost automatically more disruptive than anything that doesn't. (Note the cost-effective requirement, which is important.)
Uber, Lyft are in the "self-driving car" category, not in the "more resource-efficient car" category. Put another way, they conserve a resource (attention) that is far more scarce than fuel, cash, etc.
I use Uber when I'm in SF. It seems like a very San Francisco specific service. I would never use it in NYC because I've never had problems getting a cab and the cabs already take credit cards. I would also not use it in any other city I've been in the USA because they are so spread out I always have to have my own car, anyway.
Uber mostly seems like a better way to hail a cab in SF because hailing a cab there was previously next to impossible.
I am not sure how relevant it is in other cities but it will be interesting to see how they do.
If you think the only city that is difficult to hail a cab in is SF, you are sadly mistaken. I can personally say Austin, Atlanta, Baton Rouge, New Orleans, Athens, etc. desperately need a better way to hail a cab.
As Jared touched on I believe all 4 companies mentioned (Uber, Lyft, Tesla, Zipcar) are all "world-dominate-y" ideas, they are just in different categories.
In addition to the "can't find a cab" problem, Uber & Lyft sell experiences. This user experiences will be their biggest asset as they expand into other cities.
