Well, we already have a mechanism in place for grouping nodes: the Keyword nodelet. Right now, it's highly underutilitized, and would need a bit more additional functionality to make it work right. Namely, it should be up to the author of the node, as well as possibly editors and gods, to remove or modify keywords that are suggested by others. There would also need to be some way to search on keywords only as opposed to what is offered in Super Search
. But using keywords effectively would make organizing the site in a meta fashion work much better than trying to add yet more functions.
Dr. Michael K. Neylon - firstname.lastname@example.org
"You've left the lens cap of your mind on again, Pinky" - The Brain