OK, I’m going to keep it short and sweet this week. Trust Rank is like an “Old Boys Club”. Depending on how well connected the sites that link to you are, the greater your trustrank will be. In the same way that being connected to the old boy network at Oxford or Cambridge can really give your career a boost, being linked to from a site within this sacred inner circle can really make a difference to your rankings.
Sites that are identified as part of the inner circle are actually evaluated manually. Trust rank effects sites that are directly linked to from these trusted sites, but it doesn’t stop there. It continues to flow through the sites that are linked to numerous levels down. It’s a bit like if you went to Cambridge there is a good chance you will land a high flying job, however if you know someone that went to Cambridge you may also benefit by landing a job within the organisation they now manage and then so might your friends. Trust rank implies the better your connection to the “seed” of the trust the more you will be trusted.
The classic example of a “seed” site is the BBC from which a link would be huge endorsement of your website and place you within a trusted network.