I have observed that many ICOs that have a signature bounty campaign end up not being worth due to the huge number of participants. I think that ICOs should limit the number of signature participants to avoid a disappointed community. ICO campaign managers could probably advise their clients about it.
I have seen only one ICO at the moment that provides a limited number of people in the signature campaign and also a fixed payment in USD for each rank. I think that is a fair way of promoting for everyone.
On the one hand, it's more profitable for developers when more participants write about their project for the same expenses. But if they do not make the rules more fair, most of the participants will simply stop participating in the bounty at all.