Update: Looks like I spoke too soon. I managed to get about 10 people in before the icon disappeared. I've managed to get most people who requested a Plus invitation in but there a few left still. Again, if you want one and have a bit of patience, let me know and I'll do what I can to put you through.
Looks like Google is allow Plus members to invite people. There is no loop hole required this time.
I don't know how long this will last but if you want one, e-mail me at at email@example.com sooner rather than later. Or if you know someone who has Plus, beg for an invitation from your friend.
Exodus from Facebook continues.