...
If participants consciously go to work in the same campaign with a fraudster (to advertise a service that is probably also fraudulent) then should participants be tagged?
When it is proved that a new project is fraud and will be announced in the thread of the bounty, all new participants and those who continue to participate in the bounty should receive a negative tag.
Who should announce that a project is a scam?
Scams are not moderated in the forum. Any announcement regarding a scam is not official.
Look at this as a sample:
https://bitcointalk.org/index.php?topic=5184340.msg53109889#msg53109889Members of the forum have the right to give any other user negative or positive trust. It's their right and no one can force them to change their mind.
You can give negative trust to anyone you think is a scammer and anyone promoting a project you think is scammer. It's your right.
But in my opinion, generally it's not a good idea. It is never officially announced that a project is scam.
Assume that you believe that a project is a scam and I don't agree with you. What should I do? I don't know whether I should participate in that campaign or not. On the one hand, I don't think the project is a scam. On the other hand, I'm afraid I get negative trust from you.
Anyway, As I said, members of the forum have the right to give negative trust to any other user that they think are harmful to the forum.