I think I would like some kind of virtual experience where I have my own Memory Palace, the method of loci, the visual virtual space in your head where you walk through as you recall things. But not just for recall, for construction too. I would invite other people in and they help me build it and I help on theirs too, we build them together.
A Memory MUD. Or Memory Moo.
I wonder if this is some terrain where Spritely is going? That would be rad.
I like Emsenn's website, it has a bit of a MUD-feel. They were also writing a personal MUD engine at one point where the aim was to recreate the personal wiki approach.
Lo and behold! There is a research paper on collaborative memory palaces, from nearly 20 years ago: iScape: A collaborative memory palace for digital library search results.