I wouldn't be surprised if some of these are actually the same person or the brother/father/mother/wife of each other. In some places, 1 BTC is actually worth years of their salary. Spamming all day for this prize really pays off.
With 4000 posts in a month, I wouldn't be surprised if it's the exact opposite this time: the entire family uses the same account to spam. I'm glad Yobit wants them so badly, I hope they continue this contest to keep'm there 
This contest of highest post count is over but the promotion of 1000 sat per Post is still active. They will keep some form of incentive for posting to keep the forum alive forever and spammers happy.