The tradeoff between verification/validation and openness is definitely a tricky one. I'm the co-founder of a crowdsourcing platform prolific.ac and we settled

The tradeoff between verification/validation and openness is definitely a tricky one. I'm the co-founder of a crowdsourcing platform prolific.ac and we settled on system with minimal verification (via sms) with background screening and shadow banning. It's been effective so far at limiting bad actors though I think there are definitely some more effective ways to address this problem.