I definitely think it would be worthwhile to determine if something even "could" be done to curb that market. I'm not sure you can. Hence, why it doesn't really bother me - perhaps you can't stop it.
I'm not suggesting anything be done about upvote bots. Downvote bots, however, that's a scary precedent! However, I guess one can already buy the delegated power to downvote someone...but at least that's not anonymous.