To say that someone should not have trading experience to be in the DefaultTrust network is ridiculous. If they have no experience trading then what would they be doing looking at marketplace threads where the scams are going to be taking place?
No, having trading experience shouldn't be and is not a qualification for being on DT.
What would they be doing looking at Marketplace threads then? What incentive would they have to have to be reasonable with individual trust ratings? If they have no trading experience then why would they have sent any trust ratings?