Critically, it doesn't have to be binary trusted/untrusted, and it doesn't have to be statically determined. If Bill vouched for you yesterday and today you are trusting a bunch of discovered bots, that would down weight the amount of trust the network has in Bill a lot more than if he vouched for you did months ago.

The question is whether we can arrive at a set of rules and heuristics and applications of the system that sufficiently incentivizes being a trustworthy member of the network.