At some point they need to turn a profit, right? But what profit can they expect from their user base?
I can only think of website rankings: according to worthofweb.com, their value more than doubled in less than a month. I don't think it's working much though, it's now worth 5 times more than worthofweb.com/loyce.club, while I didn't even try 
This promotion is not just for crypto talk. The singature bounties from here as well the paybypost bounty in crypto talk forum goes into the wallet of yobit.net exchange. i.e. anyone participating in these bounties need to have a yobit.net account.