Baby boomers are joiners. They joined clubs and groups when they were young, and they stay attached to their groups. Their parents, the products of a by gone era of community groups and occupational associaitons were even more dedicated to the idea of networking through after hours social events.
Not so Gen X and Gen Y. These people have been raised in a period of easy technological connection - mobile phones, emails and mass media. In the absence of strong ideological bonds via politics and "causes" they have found eahc other in new ways. They have friends, and lots of them. They make these connections at school and keep adding to them as they grow up. They live each others lives, and engage at a social level 24/7.
While the baby boomers sought their soulmates and their comrades, brothers, sisters and peers; Gen X and Gen Y already knew who they wanted to be with - their friends. In the absence of polarising calls to action by the society, and in the face of a general loss of focus over community issues, they chose to shop, party, converse, engage and share secrets because of the bonds of friendship.
In this way they are fulfilled. They don't need clubs and associations. They are always connected to their peers, talking about their generation, arguing the toss and staying in the zone. While older people need to gather in groups to develop their personal and professional qualities, Gen X and Gen Y are already there.
So, what does this mean for the 100+ T&L associations?
It means that the groups that will survive are the ones that (1) have an independent income stream separate from basic membership numbers, (2) have some real differentiation between social networking and professional development and (3) have the ability to blend into the Gen X and Gen Y culture using social media and topical conversations, and/or (4) are able to merge and grow through amalgamation and alliances.
Clubs, unions, associations and the various social networks that do not survive will not outlive the decline of the baby boomers - once they are retired and gone, so are the non-adaptive groups they supported. They may shrink to hard core few, huddled together in bars and over BBQs, commiserating with each other about "the good old days".