If a bounty has more than 2000 participants in each campaign, stake based bounties are making no sense anymore, because everybody would get a tiny bit of tokens. In such cases fixed allocation with limited participation is much better.
i don't think, i'm prefer to join in bounty campaign with stakes based, because is fair, people who join in early time they get more rewards than people just joined in lately time.
and the reward is based on our work, but like you said sometime people who not work got their reward and it's not fair