You can absolutely drive for UberX (not sure about UberBlack) and another service. I work for Flywheel, an Uber competitor, and we regularly see people who drive for UberX, Lyft, Sidecar, and us all simultaneously.
Uber and Lyft, the big players, definitely push more passengers than smaller companies like we do, so drivers do tend to congregate to them. Passengers, though -- there really isn't much of a network effect. Lots of services in SF can get you a car. Your friends using Uber doesn't make the service any better or worse for you.
And some people do hop services. I think that there are people who use UberX most of the time, but hop to us when Uber is surging.
I think that most of the lock-in you see has to do with marketing and funding, though. Uber and Lyft have both been funded to the tune of a quarter-billion dollars. They get in front of a lot of people who haven't heard of the smaller players. The broad "get a ride with your smartphone" space has: Uber, Lyft, Sidecar, Hailo, TaxiMagic, InstantCab, us (Flywheel), and several other people taking a go at it (Yellow Cab has an app, for example). I don't think it's particularly destined to be a monopoly.
You are right about lock-in, but there is a significant convenience factor. I mean network effects as in eBay (more buyers, therefore more sellers, GOTO 10), not like Facebook (i.e friends).
If Uber has the largest fleet it really makes it hard for other services to compete as no one wants to check multiple apps for that (and the existence of aggregators a la Kayak needs some sort of open API, which I don't think exists).
Uber and Lyft, the big players, definitely push more passengers than smaller companies like we do, so drivers do tend to congregate to them. Passengers, though -- there really isn't much of a network effect. Lots of services in SF can get you a car. Your friends using Uber doesn't make the service any better or worse for you.
And some people do hop services. I think that there are people who use UberX most of the time, but hop to us when Uber is surging.
I think that most of the lock-in you see has to do with marketing and funding, though. Uber and Lyft have both been funded to the tune of a quarter-billion dollars. They get in front of a lot of people who haven't heard of the smaller players. The broad "get a ride with your smartphone" space has: Uber, Lyft, Sidecar, Hailo, TaxiMagic, InstantCab, us (Flywheel), and several other people taking a go at it (Yellow Cab has an app, for example). I don't think it's particularly destined to be a monopoly.