I am a fervent advocate against their use at all. I see the sentiment of @aggroed as a cop out in addressing the root of the problem. The problem is the culture. That is what needs to change.
Bid bots do not resolve the problem of circular voting. The same voters could just vote using the bots and now the circular voting is concealed. It's not even a band aid to the problem but rather could even be used to perpetuate it.
I say this knowing there are bot owners that I respect personally but I in no wise endorse the the use of bid bots. If we do our duty to properly curate, we have a reward already. Not merely the curation payout but the satifisfaction in knowing we performed a function intended to improving this blockchain.
Steem is our mural folks. It's up to us whether we make it truly beautiful or become a paid advertisement. Your vote and activity determines this.