It's an upsetting paradigm that's developed. I can't speak to the percentages with any accuracy but I'm sure the number of users who do this is quite high - and I understand the draw, as the real life benefits of a front page post can be massive sometimes, and sometimes even result in non-reddit media attention.

If I was a multi national corporation doing this, I think it would behoove me not to simply buy 10000 upvotes - but, and i'm sure this happens, buy just enough to get the eye of the average user and then let the reddit hive mind pull it up the rest of the way.

Whatever the extent of it, the hidden nature of the "advertising" is unnerving, if not inevitable. Unfortunately Reddit doesn't really have a short term profit motive to stop such services as they no doubt draw further attention to reddit.

now, call me a conspiracy theorist - but after watching the video of the guy who bought upvotes, I think the banning of his account feels less like the righteous banning of a vote buyer and more like the suppression of a dissident, as his video seems to have been intended to expose rather than profit.