I cannot state either way about the number of account farms that operate and how many have multiple accounts enrolled but I hope campaign managers stay vigilant against abuse.
If there was any real way to get factual data surrounding the number of account farms that exist and how many of those accounts were enrolled in campaigns pre-mixer ban (compared with today), would be interesting. If one puppeteer is operating 5 accounts at the rates you stated they would be very happy. With the exclusion of mixers, they will have to step up their game if they want to remain relevant and try to join as many campaigns as possible without getting caught out.
Think of a quality signature thief.
When mixers were good he or she may have had 5 mixers with 5 alts making $750 a week.
If you really ran signature farms well and made 750-1500 a week.
You are far less likely to switch all of that to altcointalks as the mixers will pay about 40 and account
or 200-400 a week.
So I think some major signature farms are gone. This would drop us way down in posts.