As I see it, voting bots are the equivalent of boosting a post on Facebook, or at least should have the same effect.
They are a convenient way to make one of your posts more visible, and are, just like on Facebook, more useful to those who haven't developed a large following on steemit yet.
At the same time, voting bots do influence the distribution of rewards.
I haven't looked into the paid voting bots subject, because I decided not to use them and take the long journey up (for full disclosure busy.org upvotes my posts when it 'remembers' and one of my followers enlisted me to some upvotes pool, for which I have no intention to pay anything).
I believe in the simple idea of upvoting something you appreciate, you found value in.
Voting bots, maybe even curation trails... they mess this idea up. But... according to the laws of free market and the rules that govern this ecosystem, they have the right to do so.
What advice I would suggest to serious voting bot creators/operators, would be to limit the vote submissions from the same account to one per day (and perhaps check the blockchain to see if the account submitted a different link to other voting bots as well for the same day). What good would that do? People will become more careful about what they submit to voting bots + those who create a new post every 5 minutes will not have the opportunity for multiple submissions per day compared to those who write a post in 3 hours.