I think this is too limited. If you have to wait for a DT-member to be scammed before a scammer can be tagged, many innocent Newbies will be scammed too, while doing a small deal to work on a long con doesn't mean someone can be trusted either.
As an example, look at the red trust I left. Before I was on DT, it was mainly for users who cheated my giveaways, or (the first one) a non-paying faucet). After I was put on DT (around March this year), I've tagged a couple dozen users, and none of them scammed me. Since scams aren't moderated, DT is the only protection this forum has.
Maybe i failed to give a proper explanation. the point here is not that a DT member himself has to be scammed, the accusation it self has to be based on a scam action. so if a newbie gets scammed by xyz and you tag that xyz member for scamming, it is a very valid tag. this goes for all trading related matters, call it scam/cheat/ponzi/rip-off it does not matter. as long as it's not " this guy is stupid/troll , so i gave him a negative trust because i can".
If you don't like the trust system, set your own trust list. I still haven't done it, because I prefer to see users as most people see them. But feel free to start promoting custom trust lists, if enough people agree, DT will become less powerful.
i discused this with suchmoon but i will explain it again, the trust custom lists is only good for my own use, it does not reflect how other members view my profile. since you are a DT member then you are on everybody's list by default, if you were to tag me now, even if i would exclude you from my list, everyone else by default will see your tag on my profile.
so the trust custom list does not serve any propose on this matter.
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even if we are never going to have any rules, i hope that the reasonable DT members will stand against those irrational tags when they see them. like that DT member who stood up for cryptohunter when he was given a red tag for being a "troll" and gave cryptohunter a positive one because he thought that being a troll does not qualify you for a negative trust of which i am sure that 99% of members would agree to that . i am by no means defending the "way" that cryptohunter went about the "gang" and all the exaggerations ,but it was sad to see only a few DTs disagreed to that and actually only 1 took an action while a few others supported that irrational feedback.