Jamaica has had this system for years. You stand next to the street and point if you want to go up or down, and you get a ride for $1. It's pretty cool. 7 people in one car at times.
Lebanon has a similar thing. Stand by the highway, get in the next private bus/van that comes by, pay the driver $1-$2 when you get off at your destination. You can go anywhere in the country for $2; it's amazing.