In the original barter economies, it was difficult to find someone who had something you want in exchange for something you had, but now there are much more efficient ways to streamline that search process.
As to the potential value, to tsotha's question, this is very philosophical. Some will see it as valuable, others will be terrified. For me personally, I like not being too abstracted away from what I'm producing or consuming.
Gambling uses chips because chips are easier to give away than money. Using that logic, at least for me, giving away money is easier than trading something, especially if that something I have created and poured my energy into. The transaction without money then forces me to think about true utility and value, and would greatly discourage conspicuous and contrived consumption.
What they actually end-up doing is competing the incumbent services in a fly bellow the radar illegal operation which actually makes the taxi drivers themselves poorer while diverting most of the extra cash to the ring masters.