I got a message from new member who requested membership in the beginning of December. She hasn't got her invitation although it was sent on 6th. There were few others whose invitations were sent in the same period and who haven't replied to it. To be sure, I sent invitations again to all persons who have requested to join two weeks ago and haven't replied yet. We're not closing sign ups, I think there might have been a problem with Blogger or spam guard.
I check my mail every day and send invitations once a day. You should get one in two days after requesting to join. I've recently changed the e-mail address in the sidebar, because I started to get spam to my personal account, so I'd ask you to use the sidebar address from now on.