[eridius]

This is not true. Users and drivers benefit when the number of drivers and the number of users are in a good enough balance, such that there are enough free drivers on the road to be able to have one near to each prospective user, but not so much as to be wasteful.

But the absolute numbers of each do not matter. Adding more drivers does not benefit existing users if more users are added as well to cause those drivers to be active on trips whenever a new user tries to book a trip. And adding more users without adding more drivers is, of course, bad for the users, because it produces a scarcity of cars.

This is pretty much wholly unrelated to the idea of network effects.

[robrenaud]

Even if the drivers/users ratio is constant, raw #drivers does matter, given a fixed amount of space. As you get more drivers in the same amount of space, the minimum average distance from a user to a driver decreases.

[eridius]

Any driver that has a passenger is, for all intents and purposes, nonexistent when it comes to new passengers placing calls. You could have one million drivers in SF, but if 999,999 of them are on an active trip, and only 1 driver is free, then the fact that there's a million drivers makes no difference whatsoever.