We at @moonbot have a subscription based model for upvoting. It's a small upvote amount over 30 days. If someone were to implement this on a higher scale ( which we'll be doing soon ), it might be a worth option for people. It solves the only use bots for monetary gain issue. It is a clean system ( no comment spam back ), and you ( the end-user) doesn't have to do anything for a whole month. The bot just upvotes your content for a whole month. Bots, will always be around. It's a matter of which kind can you stomach.