Wang Xiangyu started driving for Uber Technologies Inc in late June. Soon enough, he received his first order from the car-hailing platform. But to Wang's surprise, the "passenger" was not looking for a ride.

Instead, the ride-booker wanted to know whether Wang wanted to "get an injection", a popular metaphor for helping drivers trick Uber into paying out cash for fake trips. The San Francisco-based company is spending heavily on free rides and driver bonuses to establish its presence in China.

The ride-booker said Wang could pretend to take her on a route. When the so-called "trip" is over, she would pay Wang 50 yuan ($8 ), the value of the coupons Uber hands out to new passengers. In return, Wang was to pay her 25 yuan as commission.