Trust system is nothing. I am here for 5 years. You can give negative trust one of a scammer then he creates a new account and scam anyone. Easy. Trust system is just for trusted members gang
Except that most people don't trust a recently registered user. They may trust a Sr. Member/Legendary, however.
That's why neg trusting him (in case it's needed) is important. Bam, now he needs 775+ activity and 1000 merits to get as many 'reputation' as he had.
In this world, you cannot trust anyone even Satoshi. Because he created bitcoin. Why? Because we need trustless systems. Why? Because no one is trusted