@OnTheWayOut, great point. I'd like to add that to the group I went, every now and then there would be some people who were more into support and recovery as a lifestyle, wanting to share and make the group something that was not. One lady was convinced that she needed help because she was hypnotized and when she "came back", she didn't completely and wanted the group to help her recover the part that was missing. Another guy wanted us to help him get his wife back that left him for other guy and he claimed that it was "mind controlled by him", and we could help him.
However, those were two out of a rather large number of people who had real stories, real needs for support, and real family members that they lost to cults, some of which had not been in touch with them for years. I don't want bad apples to be discouraging to the idea.
Not sure if there should be requirements or some kind of intake to improve the quality of the group, but there should be a plan for people who may want to make it something out of its scope. When groups are open to the public, high chances are that there will be people with no business belonging to that group coming to it for other reasons. I've seen that happening. At least, have a great facilitator that can make the group and the conversation remain on point and within scope.