For Credibility it would be based on the thanked/# posts ratio, and on the number of download views. For Loyalty (trusted level) it would be based off the Vouch system, and as with the current Vouch Subsection: a minimum of $5 is required.
If we catch members faking their vouches in any way, they will be permanently banned or their Loyalty bar will be set to a negative score.
I am sure this would scare off most members, and the risks are there if they decide to do this anyway.