Well nothing will be mandatory, I basically wanted to give regional groups the option to develop their group more than just a group forum category by giving them the facility to have a calendar and people in charge of meetings/events if they want to do this. If you have a group of 20 or 30 you might want to pool some funds for local events or to have someone come give a workshop etc (so i mentioned treasurer).
As for growth I think we are growing a little too fast these days with usually over 20 new registrations a day. The rapid growth resulted in me moving to apug full time because I simply couldn't handle apug as a side project. I think 5-10 new signups per day would be a good number but it's not really something I can control. I suppose if things got out of hand and the membership were unhappy we could vote to lock down the site to subscribers only. I think this would have many negative aspects such as shunning 1,000's of film enthusiasts from the site and the cause behind it. I like having our forum content all over the search engines and freely available. I think continued growth is good for our craft and if this many people are signing up a day we'll all be able to shoot film and buy paper for a long time. Showing up every day to 600 new posts may get annoying for some but it's exciting for me, it means traditional photography is still a huge force to be reckoned with and we are alive and kicking