Web of trust should work both ways - not just for showing you notes in your web of trust but warning you about users fpagged by members of your web of trust.
In my web of trust clients I only see notes from people I follow or people that they follow.
It would be good if my clients also displayed an indication if someone I followed had marked someone as spam or scam.
Decentralised trust filtering should work both ways. For both positive and negative filtering.