Steemit is the most transparent shit I've ever seen! Everyone is able to follow every single transaction, comment or vote.
Maybe for some people those bidbots are a problem but the most annoying problem is the spamming on posts one spent money to promote them.
If you REALLY think the kind of service is useful (the people see it AFTER they read the posting - not before) you might design a browser-extention for firefox or chrome is exactly your strategy.
You might open the post to check the votes or follow the transaction in the blockchain. Just compare the the link people hit (or found in the html as a link) to your list of perm_links got from transaction and add something like "promoted with $$$xxx) after the link.
So everybody is free in decision to use it or not!
And the people see your information BEFORE they open a link. Not after they read it!

Thats easy stuff - you've done on a weekend.