AMA has ALWAYS been composed of old people. I joined when I was 10, and I thought I was surrounded by old farts back then!

I really doubt that is the reason why many don't join. When I was younger, the college had its own RC club with its own insurance setup on school grounds. Those that stayed in the hobby didn't join AMA until they graduated. (shrug)
Slightly off topic, I just wanted to direct you to a "Park Flyers" forum thread of what true Park Flyer
modelers fly:
http://www.rcgroups.com/forums/showthread.php?t=448751
I posted this mainly for Stickbuilder's benefit. More sticks than you can shake a plane at!
Getting back ON topic, I agree with ptulmer that the "fence-sitter" Park Flyers will become more interested in joining AMA when they start feeling the squeeze. One possible reason there are so many AMA members at my park is that there are VERY few open parks to fly at in the Bay Area. I've been thinking that AMA and Park Flyers will join forces like fuel and air in a Diesel Piston...just need enough pressure!
1. AMA's dwindling membership of the Old Guard will cause it to change its structure to better support Public Park Flying. Already starting to happen, though I think the e-ticket proposal is a "false start."
2. Public Parks steadily get closed as city officials take the easy route to prevent lawsuits until Park Flyers start organizing themselves in order to keep some of the fields open. AMA will be the easiest method since it is already established and already has relations with FAA, FCC, Insurance, and government officials. Already starting to happen as more Park Flyers start seeking other flyers for help and more clubs have members pick up Park Flying on the side and meet up with the others.
We'll meet in the middle in the darkest of times. AMA will have to adjust, but so will the Park Flyers as they realize they'll need the structure and safety regulations of a chartered club if they are going to get ANYTHING through the city council.
I'm glad that AMA is already putting in an effort, but I think it needs a more flexible insurance structure and more commercial visibility, rather than some discounted, stripped membership card. AMA has pulled off some amazing stuff in the past, so I'm confident they'll find a solution.
I think there are many Park Flyers that already have the proper mentality to being good supportive members of AMA. Many just don't know enough about AMA to feel a need to join. That's just a matter of the current members getting the word out. As for the rest of the Park Flyers who think AMA and the chartered clubs no longer serve a purpose and will perish under the weight of the new "wave" of $30 foamies....enjoy that open park while it lasts.
Hey! I can idea! Let's go buy a bunch of paintball guns and go have a game at the park! Wha....what do you mean I can't? I bought it at a toy store, so that means I can use it anywhere, right? I have to go PAY to use it at some site? [&:]
The more stubborn members of the "Old Guard" need to understand that AMA will have to develop a plan to incorporate Public Parks since it is steadily becoming more difficult to establish leased Flying Sites. The Clubs in my area are awfully crowded already. Those parks will give AMA a new source of members and help to make this hobby grow. If AMA's numbers drop enough that they become too small a percentage of the population to be relevant in the eyes of Government officials, than there could be nasty spiral effect as neighboring residents petition off one field after another due to noise and perceived danger.
However, the Park Flyers also need to understand that it's just a matter of time before the Park Flyers get the same restricted treatment as the dogs, skateboards, paintball guns, and what have you. We're going to need the representation of a large membership in order to be heard. The current flying sites were not established by having 3 modelers say "pretty please" to the city council, y'know. They came in as a members of an organization of thousands of modelers with an established history of hundreds of successful flying sites. We're eventually going to need that. You might as well prep for the day when you'll need to organize a club and follow safety procedures in order to utilize a park.