This group existed for our developer to populate via an external program, so it wasn't via a user promotion - the idea is that we had pairs of groups, and after an event, the developer would add them to one group associated with the event, and then I'd send them a welcome letter via the ACP, and move them into the permanent group for the event (if that makes any sense).
I'm on this one. Manually, and hoping it's not a ton of people....
-S-