Some years back, someone posted official-looking signs around the Stanford campus containing a "confession" from the bookstore admitting that it had been gouging students for years and offering them refunds.

The bookstore had to hustle to get out its own signs telling students that this was prank and that no refunds would be issued.

I normally don't condone pranks but this one was pretty clever and it did send them reeling for a few days anyway.

Anyway, it is probably students' pent-up frustration in feeling trapped by this system that is the real "secret sauce" behind the success of this service. Lots of demand. All that was missing was an elegant solution.