I still don't understand how trust works. I've been reading related threads and only have the vaguest idea- is it a sort of up vote/down vote thing related to doing deals between members?
Can someone point me to a comprehensive explainer of the whole trust system if such a page exists?
Basically, people can up vote/down vote other people's accounts. It usually happens after you trade with someone. If the deal goes smoothly, you can give them positive trust. If the deal goes sour because they scammed you, then you can leave them negative trust. There is also an option to enter the risked BTC amount. If you sold a miner to me for 1 BTC and I gave you 1 BTC, that's the amount that would be "risked" in this transaction.
However, if I were to give you positive or negative trust, very few people would notice it because I'm not in what's known as the "default trust list". The same also goes for you. Unless someone specifically chose to add us to their own trust list, the trust that we give to others (either positive or negative) would only be viewable if you clicked on someone's trust history and enabled the option to show untrusted feedback.
When you add someone to your trust list, their ratings suddenly become visible by default without the need to do the above. Most people here use the default trust list. The ratings of those who are in this list carry a lot more weight than others because their ratings are, you guessed it, visible by default:
http://bitcointalk.org/index.php?action=trustNotice how there are different depths. When someone from depth 1 adds another user into their trust list, they become part of depth 2. The trust ratings from those in depth 1 carry more weight than those in depth 2.
Now click on the "heiracharial view" link at the bottom of the page. Assuming that you are using the default trust list (i.e. you have DefaultTrust in depth 0), you'll see that DefaultTrust "trusts" theymos who trusts gmaxwell. Hence, DefaultTrust is in depth 0, theymos is in depth 1, and gmaxwell is in depth 2. If theymos trusted me, you would see my name in depth 2 alongside gmaxwell. The trust ratings that I give to others would then suddenly have much more weight in the community because they would immediately become visible by 99% of the members here who don't change their trust list.
As another example, if I removed DefaultTrust from depth 0 (and therefore remove theymos and all the other people currently in depth 1) and added a troll who likes to give negative ratings to reputable members (or even if I added a legitimate user who added such a troll to their own trust list), suddenly the trust ratings that I see in the forums would be all wonky and normally highly trusted users such as theymos, gmaxwell, dooglus, Stunna, Tomatocage, etc. might suddenly be showing red trust and the "Trade with extreme caution!" tag next to their profiles.