There is one more important con: reputation. You can inflate your rep basically by combining being in a perpetual state of powering down and pumping around the same money over and over. The older the max allowed age for a bot, the faster you can pump around the same money, the faster you can artificially inflate your reputation. My rep on my primary blogging account is 56 after over a year of blogging my fiction. 52 on my dev account that is a few months younger. There are bot-using spam bots half the age of my youngest accounts that already have close to 60 rep to their name without it seems even one single genuine upvote as far as can be quickly assesed.
The big problem with this is that ik makes self regulation a big problem. If I were to spent all of my voting power to flag a spammer for a week, I'll cost that spammer two maybe three dolar at current rates. I'll know though that because of the bidbots, my flags wont put a dent in their rep and likely in a few months that spammer will have a higher rep than me and will then be able to flag me out of existance in retaliation. Result : I (and others that would be tempted to fight the spam) will think twice before using my SP to try and help clean up the platform. It is cool that there are powerfull initiatives like @spaminator, but even @spaminator has only 66 in rep, a rep I think not unachievable for a persistent bid-bot user with some funds to pump around.