The Second Life group proved not to be very popular, because there's a limit to the number of groups to which you can subscribe (42 groups). The Subscribe-O-Matic group did not have this setback, but the only way people could subscribe was by touching one of the panels on my sim. I could not invite people by menu or by sending them a URL or an object, and most people didn't notice the panels.
Do you want to unsubscribe? Just touch the panel on my sim (see picture above) and your name will be removed from the list.