Funny, I was thinking the same thing. I think that's because there were two mentions of Plan 9 in one day. Otherwise, we only see it every few days or so.
I was inspired by one of the users' puzzlement over Plan 9 over at the Scheme 9 interpreter thread to post this paper, since it explains the core concept of per-process namespaces.
And since no one else had done so before, bafflingly.
Also keep in mind that Plan 9 has involved significantly since the publication date. 8 1/2 and WORM have been superseded by rio and Venti, the 9P protocol is a bit more extensive, ndb and /net plus the auth subsystem have become more prominent since then, etc.
