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 that is possible since 2000 people in a single bounty campaign since the manager had to limit the campaign in order make payouts more reasonable for bounty hunters and also properly manage the camapign and besides i don't see any ICO/IEO campaign here on bitcointalk holding a 2000 or more partcipants and if so, the trusted dts and moderators would have notice it and shutdown it