Blizzard says in the upcoming WoW Expansion pack "Wrath of the Lich King" higher lvl players can give other players who is too low lvl for a mount a ride, at both flying mounts and land mounts. It kinda works like a taxi.

And I thought that this actually is a good way to get rid of beggars or other annoying players... As long as you`re a paladin or priest.