I jus came across this on the forums and I thought I should share it here. It have no revelence to botting in general but a blue response may have some useful information. The below paragraph is a copy/paste from the blue.
"So what we've done is developed a hidden system that tracks player behavior in matchmade groups on a number of different levels. We don't go into a lot of details about the system for a few reasons: A) we've been constantly evolving how intelligent the system is, B) the system is dynamic so that it can apply penalties based on varying factors -- it's analyzing trends as they change over time and accounting for them in some fashion -- and C) we don't want players to know exactly how the system starts penalizing people for less-than-average behavior and then try to game it."
Source Blizzard says it's ok to be a jerk - Forums - World of Warcraft
"So what we've done is developed a hidden system that tracks player behavior in matchmade groups on a number of different levels. We don't go into a lot of details about the system for a few reasons: A) we've been constantly evolving how intelligent the system is, B) the system is dynamic so that it can apply penalties based on varying factors -- it's analyzing trends as they change over time and accounting for them in some fashion -- and C) we don't want players to know exactly how the system starts penalizing people for less-than-average behavior and then try to game it."
Source Blizzard says it's ok to be a jerk - Forums - World of Warcraft