I don't get doing this. I feel that this hobby is relatively small and sharing information among collectors is very beneficial. It looks like the general discussion forums from each topic heading are gone if you are not logged in as a member. From Common Poster Subjects, the topics like authentication and restoration are not accessible.
Regarding the authentication, I know that MPT, MPA, NSFGE and this forum, APF, have saved me money over the years. If the information on this forum, helps keep even $1 out of the hands of poster forgers, then that is a positive contribution to all collectors.
Everyone has to start somewhere, and restricting the flow of information may force people to seek it elsewhere. I like to test drive forums before I join. I bet some people that started out as guests eventually join and contribute to the forum.
This action seems excessive to mitigate the complaints of the Mid-Auction analysis forum. If that topic is not worth the headache, then burn it down, but don't shut guests out of the wealth of knowledge and experience of all the members.