1. This exact program they're launching helps build a barrier (subscription)

2. Uber Pool requires a large number of drivers and customers to make it work. This is a real network effect and benefit, as having 2-3 customers in a car is more efficient than 1. This requires having other customers on a similiar route.

3. Customers want the closest car to them, meaning the company with the most cars gets a benefit

4. There are driver and customer acquisition and switching costs