fivethirtyeight mentions one obvious usage: providing it to city planners for say bus routing.

The other thing I think you could do that would be very useful for drivers is show them areas that there are typical long waits / longer rides right now. I know a lot of drivers do some planning, but they seem to be in the dark. I'm sure a 'where to uber' app on android / ios for drivers telling them when to get where to take advantage of surge pricing for customers that will want to get taken to a desirable spot would be VERY popular among drivers.