Six to eight months ago selling a vote was a mortal sin ;)
Only a few services existed for the actual / real purpose of postpromotion.

The problem with bidbots and vote buying is not that they exists.
On one hand it has become the only profitable business around, this has increased the demand for delegation leases and drove the price of delegations higher thus drying the organic vote SP pool.

The second one is that we spend too much time working on blacklist, because of the poor use comment and post farmers are giving to the bots, if we spent that time doing a whitelist instead the farmers will go somewhere else or try something different..