allow anonymous post to organic groups
I wasn't able to make this work, so I ended up setting up a "fake anonymous" user in its own module - a bit of a superhack that I'm not happy with.  That said, it works.  This "fake anonymous" user id is set via an admin settings page, and gets added to every group created.  When new posts are created I added a form hook to change the author to this "fake anonymous" user id if the submitter is anonymous.  Maybe this is easier in D7?