I thought the whole point (of the post) was the network effects can effectively be bootstrapped from the mobile phone book. if all drivers (who aren't uber emp

I thought the whole point (of the post) was the network effects can effectively be bootstrapped from the mobile phone book. if all drivers (who aren't uber employees) and all users can be part of multiple networks (bootstrapped from mobile phonebook and almost zero cost to both) how can uber maintain a dominant position?