[mikeash]

The drivers are offered a certain rate. They refuse, implicitly asking for a higher rate. This repeats until the drivers get a rate they can accept, or they give up and go home.

On the other side, passengers are offered a certain rate. They can accept it, or they can refuse and implicitly ask for a lower rate.

[eropple]

That seems less like a negotiation to me than a double-dealing bookmaker. ;)