Personally, I think that it is probably not a bad idea to have DefaultTurst in your trust list as it is a good starting point as to whose ratings you should trust. As you spend time in the various marketplace sections (as well as other parts of the forum), you will be able to determine who is reputable enough to have in your trust list, and add them to your trust list (even if they are already in your trust network), and will see who is leaving trust ratings that you do not believe in (and are in your trust network), and exclude them from your trust list. Over time, you will have a trust list with a lot of exclusions and a good number of people in your trust list. If you have been around long enough then you should be able to develop a trust network that results in fairly accurate trust scores.