That raises an intriguing question--what if an MMO was developed that was explicitly designed to be a competition between programmers to write the best bots? Even if a bot exploited a bug, you could write bug-fixes, and the programmer would have to evolve the bot to the new environment.
One game like that was published in 1985, http://en.wikipedia.org/wiki/Crobots "Crobots is a programming game released for the first time by Tom Poindexter in December, 1985. The robots are controlled by a program written in a stripped-down version of C. The robot's mission is to seek out and destroy other robots, each running different programs."
I played it as a kid, was quite fun, though my bots largely sucked .. perhaps should try again now that have more programming experience :)
EDIT: seems that it's a clone of a thing that was originally made in 1970s already, "RobotWar was a programming game written by Silas Warner. This game, along with the companion program RobotWrite, was originally developed in the TUTOR programming language language on the PLATO system in the 1970s" http://en.wikipedia.org/wiki/RobotWar
You could argue that existing MMO's already have everything in place for you to play them that way. These games already have tons of different objectives and ways to play, what's one more?
The best programmers write bots that can automate lots of characters to farm gold/money/valuable items/powerlevel characters which can used, sold to other players, etc. Whoever makes the most money "wins".
