I guess Yobit should have gone through the "needs approval" route instead of paying people until they get banned. It shouldn't be a major issue tho.
Yeah, that would also decrease the workload for yahoo. I think they should add a script where users need to get approved by yahoo before they can start earning satoshis. Should not be a huge problem to do that. Or, they could go the traditional way with a spreadsheet and stuff like that. Easier to track participants and increase transparency. More importantly, the funds should be escrowed. Their last campaign didn't end well and IIRC some of the participants didn't get paid.
Do you really think YoBit concern about the quality of campaign, all they want is trouble-free campaign on Bitcointalk until their funds allotted to campaign is exhausted. Hiring Yahoo solved this problem for them and they gained little reputation to run campaign without getting any hammer from Theymos. Though, I still think current scenario is quite ok because Yahoo is doing commendable job to cut-out spammers at maximum.