Hey Adam, good eye. Groups are still a work in progress. They exist in
Wave, but aren't fully baked into the UI yet.
Hmm, I'm not sure the access control will be that fine grained, at
least not right off the bat. Looks like there's already a feature
request along those lines, though:
http://code.google.com/p/google-wave-resources/issues/detail?id=7.
We'll consider all the requests we get in our issue tracker.
I think a robot could provide this functionality, but with some
tradeoffs. There's a good (if long!) discussion on access control
here: http://groups.google.com/group/google-wave-api/browse_thread/thread/e2132221ce2ba905#.
In particular, see Jorge's comment about affecting playback.