Could we expand web of trust by having users verify other npubs?  Have a "yeah this guy's legit" button or something.

It's obviously gameable because of bots, but I think the fix is to start close to yourself in the social graph.  Assuming most of the npubs you follow are legit, how many of them appear to trust the npub in question?  Do they interact often?

The hardest part is helping new users to find trusted npubs to follow.