Rules work only as far as you can enforce them. So who's gonna enforce the rules? Who's going to have the power to remove ratings or remove people from DT?
Honestly default trust imo is just a very outdated judge of a completely different forum. More than half the people on it are dead accounts, or people who rised to the DT status by the amount of time they spent on the forums.
But if there's one thing that doesn't make sense it's completely biased judgements that are in no way related to an exchange of goods.
Like, sure, I get that someone trusts another person and tags him accordingly, or that someone else doesn't trust another. But isn't trust supposed to show the financial honesty of a person? If someone can be charismatic enough to convince 5 other members to trust him that's great, but if another person with questionable opinions had over thousands of dollars in trades is less trusted than this charismatic person... It really skews the meaning of "Trust" on the forums.