I believe Tailing not only -should- be allowed for people, but it is the prime use of it. Tailing a vehicle that is passing you is already effectively a fully manual operation, as there simply is not enough time to type the command usually.
Tailing a character on the other hand automates something that is trivial to do even manually, simply removing the propensity for typos to disrupt you. Additionally, there are edge cases where a player -is- a vehicle when using a certain item.
Finishing the code in this fashion would also open it up utility wise to be used by drones to track criminals.