Haven't participate in any bounty campaign yet, but had filled hundreds of Airdrop forms.
I get the feeling that you are forced to spam content on forums during campaigns, so that is one of the reasons why I haven't tried to participate.
On the other hand, like everyone already written, most Airdrops are scams... I got lucky with one, so started participating more often, maybe too often... not so happy right now, I have a feeling that I'm just wasting my time.
I'm reading a lot on this forum, but looks like I will have to be more active to qualify for bounty campaigns