Thanks for the correction on Eckenrode, Neal.
I will say that years ago the ASGCA was more exclusionary, and in the 1950s-1970s more or less allocated the country to different architects by making it almost impossible for a new competitor to join from the territory of an existing member. That stuff has now ended, and while a selective society, not a professional trade organization, the ASGCA is far more inclusive. Its members run the gamut of design philosophy, from Tom Fazio, Rees Jones, Arthur Hills and Bob Lohmann to Jeff Brauer, Robin Nelson, Brian Silva, Bill Coore and Gil Hanse. That's pretty inclusive.
I've encouraged Ron Prichard and Jim Engh to join, but they are simply not joiners by dint of their personal and professional character. Too bad, as they and the ASGCA would benefit from their inclusion - the same with Tom Doak. In addition to the reasoning I gave in a previous post, some are also put off by the relatively high cost of membership, plus the fact (as I understand it) that membership entails attendance at something like 3 of the first 5 annual meetings, a commitment of time and money than can be virtually prohibitive to some architects.
You could make a case that the ASGCA has encouraged a certain style of professionalism modeled on narrowly on landscape architecture and civil engineering. On the other hand, its membership is broader-based in terms of approach than ever before, and its meetings (I've attended more than half a dozen and made presentations at two of them) make a sincere effort at keeping members abreast of business, technical and legal issues that are of interest to all practitioners.
My bet is that there are many ASGCA members who are unacknowledged lurkers on this site. Maybe even on this post!