You bring up a fundamental difference between Groupon and Uber. Car riding services are actually increasing the size of the taxi riding market.
Re:In Search of Uber’s Unicorn
by toomuchtodo on Tuesday October 28, 2014 @06:29PM
(#8524007)
Only if the lower costs that enable that increase in the riding market are sustainable, which appears its not (at least until self driving vehicles are here).
What does that even mean, at scale? If it is a money printing press for everyone involved, you have to postulate either that the entire market grows rapidly (for "local businesses", no matter what they do, in this case) or you've (at best!) created a middleman to tax all transactions in the system.