Sort:  

I think that the use of bots should be intended to be used by mennows, and if used by people with a hi reputation or earnings should be limited to use only one bot.
Maybe setting a minimum size post to the bot accept the post, or a minimum voting of true people to the post to be approved to use a certain bot should be good.
Maybe 1 vote of real people to use a bot that can give 100 votes. It could be a 1% rule for voting posts. And the same rule for biding bots..

This 1% rule shold be useful to filter spam post, because they will never met the minimum required votes for real people. Or at least could limit the use of high powered bots to spamming