You're mostly talking about social media bounty here. For sure there are account farmer, its kinda become common knowledge that poeple have been abusing bounty with multiple account especially Social media bounty because it's easy to make another account and buy some follower and hope they get 90% real follower by audit, that's why KYC are required to claim the reward for some project. But bounty like Signature campaign are still good for promoting your project because you promoting your project directly to crypto enthusiast in one of the biggest crypto forum. I personally stay away from social media campaign because most of the time it's not worth it and have to many participant for the pool.