Yes. when the participants amount is high the rewards are less. that's true. But how can we filter the best participants ?. What should be the method. I think it is impossible. Only possible way is to select higher bitcointalk rankers. But guess if they choose only full members and above. then you ?. and all others ?.
It will be unfair to those have a low rank, we all know how it hard to have a merit for ranking up, so how about the jr. Members and members if all the bounty will select the high rank only.