Yeah, that's true, but it would be even better with a neutral bot that come in and said something like "this post has bought votes for XX SBD to get upvotes worth XX SBD". This will make buying upvotes completely transparent, and it will be very easy to see which posts that are heavily promoted.

This post for example has almost 500 comments, but I had not even noticed all the bots who upvoted it, because these are pretty much hidden and scattered.