That was exactly what we tried a year ago (mobile-based ridesharing).
It did not work for us because:
1) Hard to get traction due to the classic chicken-and-egg problem: Ride sharers do not sign-up due to the lack of riders, and riders do not sign-up due to the lack of sharers.
2) People do not trust on anonymous riders. We hoped to solve this issue by introducing a social network where we would prioritize the matches by degrees of separation. But that didn't work due to #1
3) The large majority of the population enjoy their privacy in their own car and do not have a motivation to share the ride (perhaps when gas prices get higher)
4) For those who are motivated enough to share a ride, there are plenty of options available out there: Craigslist, employer's bulletin board, in additional to local authorities (ex: 511.org and casual car pooling in Bay Area)
In the best case scenario this service would become popular among a certain subset of the country. It would never be as sweeping as he imagines, in the US. My money is still on mass transit + bicycles as a good solution to the problem of cars.
I was expecting robot taxis to do that one day. However, I was told that people just love their cars too much and would never get rid of them. Maybe they are right - and maybe people drive alone all the time because they like to be alone?
It did not work for us because:
1) Hard to get traction due to the classic chicken-and-egg problem: Ride sharers do not sign-up due to the lack of riders, and riders do not sign-up due to the lack of sharers.
2) People do not trust on anonymous riders. We hoped to solve this issue by introducing a social network where we would prioritize the matches by degrees of separation. But that didn't work due to #1
3) The large majority of the population enjoy their privacy in their own car and do not have a motivation to share the ride (perhaps when gas prices get higher)
4) For those who are motivated enough to share a ride, there are plenty of options available out there: Craigslist, employer's bulletin board, in additional to local authorities (ex: 511.org and casual car pooling in Bay Area)
Seems like this one (web based, not mobile) got some traction: http://www.ridester.com/