While definitely a possibility, the single farmer that gets banned then costs 5x to replace. Blizzard does track money exchanges and bans accordingly.

I think that the idea of racking up $70 a month from valid customers is too much to pass up for them just to try and stop someone from farming gold... there are too many OTHER issues.

On the other hand, it could lead to quickly outlawed applications for multiplexing leaving us with a 1:1 hardware solution only.