If negative feedback is only used to tag someone when they have already scammed, then it is useless.
It not useless. The tag then save others not to fall in the same trap. Loan default accusations are the best example.
Yes, you are right. After I wrote that I kept thinking.
It is not useless because it prevents others from falling into the same trap, but as it works what happens is that if you wait for someone to scam to tag him, what usually happens is that after being tagged he disappears from the forum.
But I will rephrase that by saying that it would be more useful if it served to prevent the initial scam.