Can you list the pros and cons that you factored into this final statement, because that seems quite doubtful bordering on ludicrous.
The utility of the trust system is quite obvious. I'm not sure if your question is real.
Without any trust system at all, scammers could keep scamming without restrictions, without even using a new account. Without any trust the only thing newbies would see is rank, so a scammer can get a Legendary account and scam a lot of users.
Without any default trust list at all, users would need to set up their own list. This makes perfect sense for experienced users who know whom to trust. But newbies don't know anybody so they would either add anyone to their list (randomly or Legendaries assuming that means the user can be trusted) or nobody. At least a list of suggestions of trusted users is required.
In fact,
default trust should be shown even to non-registered users. I hope theymos does that soon.
I think you are focusing on the instances where it is useful and missing the greater and more far reaching/dangerous issues.
Things are a LOT more complex than you may realise.
To find the REAL net gain of the DT system/merit you must take all possible influences it has over the board and its members.
You are not considering
1. The implications for free speech (HUGE)
2. The false sense of security and positive or neutral score can render
3. The fact that people should study a persons entire history here before trading not just be lazy and rely on a misleading score.
4. The damage to accounts that are not scammers but got red trust via abuse.
5. The incentive and reward to abuse it.
6. The possible benefits of a different policing system
DT/Merit is misleading, VERY dangerous for an open discussion forum, and it's whack a mole success is limited really.
We could go into a deep debate on each point. I am up for that. Just find my thread of the year here in meta and post on it. I will respond.