RE: Why does the AMA have to grow?
I'm sort of a collectivist, I suppose. The AMA is the official recognized model aircraft organization in the USA. With parkfliers, etc, there is an increasingly large segment of people in model aviation who are not AMA members. There is concern that these "outlaw" people may unknowingly do harm to all of model aviation. This is one reason. The other is that the AMA offers benefits to AMA members (sanctioend competitions, official national and world records, etc.) which are not available to the non AMA modeler.
I saw my second parkflier a couple of weeks back, flying on the soccer field next to our control line club field.