I hardly know shit about the trust system, except that I see that it is a link that I can click on in my profile.
And I can understand if you did a trade (or planning a trade)
The trust system is not just for trades. I can distrust you for any reason. If people trust me, then they trust who I trust.
Theymos picks the people whom he believes most match his morals to be on DT1. Those members pick members they trust to go to on DT2.
DT2 then decides who they trust or not based on those morals.