I do not think that the trust system holds any merit per say besides tagging obvious scammers. If you take a look at "quickseller" there trust is deep in the red but I am many others still consider him trustworthy.
The trust system isn't meant to be used as a definitive 'this person is/isn't a scammer', it is meant to be used as a reference for if someone has done something untrustworthy. If you decide to still trust someone after this, it is your choice.
The trust system does not protect users from being scammed either, look at the master-p scams.
master-p had >100 trust score when he pulled off his scams. To most, master-p was completely trustworthy.
The only thing that protects users is a trusted escrow, such as John K. ; OGnasty ; Garr255 ; Ian Knowles ; Rassah ; Ryland Rene Taylor-Almanza (These are all forum treasures holding between 250-1k BTC)
I'm fairly sure most of those are inactive or do not do escrow, let alone hold any BTC for the forum anymore. Use someone with their personal information known and verified (E.G OgNasty/Blazed) or someone that you personally trust. It also helps if you follow the standard escrow procedure and not be an ass about it.