There are many threads on the topic already; "no, thank you" to forum-sent PM spam; adding an announcement (not a banner) at the top of the page might be OK at some point once the dust settles.

But in general users should learn how the system works and not just set up lists because someone told them to. It takes time to get to know people you can trust. And some assholes try to discredit the idea of trust lists by weaponizing them.