Agreed. They wouldn't even need to be overtaken. It seems that a lot of the valuation is based on the premise that this is a global winner takes all market. If it turns out that's not true and there is in fact space for multiple competitors then the valuation could turn out to be a lot less.
If Uber has a moat of any sort to protect itself from competition, I'm not seeing it.
Once Uber has executed a tactical blitzkreig in a new city and incited a pogrom against the cab drivers, and fought the legislative battles with resistant city councils; the door is open for any rideshare company to glide in on Uber's coatails and take advantage of all that costly trailblazing without paying a dime.
Cynically: that's why Uber doesn't want to win that kind of war.
They want to get in, and then work with the locals to establish some `sensible regulation'. Regulation that just happens to be cumbersome enough to deter new small-scale entrants.
This is not true in Austin. The city passed a fingerprint and registration requirement and uber and lyft both left the following weekend. Smaller competitors are growing fast. I miss the nice apps and cheap prices but the alternatives are ok.