I expect they already do this, and also have a system for cutting off suspected fraudulent passengers. And it probably works pretty well (they have some smart statisticians there, and the right incentives), but it's statistically based and every so often they have a false positive and cut off an honest customer or an honest driver. It would be unacceptable for a government body, or a utility with a government-granted monopoly, to do this without an appeals process, but it doesn't sound so bad for a private company that has competition.