I will suggest that MetaFilter may be a victim of its own success to some degree. Growth of a forum always introduces new challenges and you solve those or experience die-back. I have seen it often, in other forums. though none were supporting multiple full time staff members.

Yes, I realize Matt thinks it is largely due to changes in Google algorithms and that may be true. Or it may be more complicated than that. (In my experience, it is more about the community. Everything else is secondary.)