Having being rather actively involved in industry associations myself, I know where you're coming from. I had a quick look at the GCMGA site and found the same problem we had in SAPCA - a good CMS site with a lot of money poured into design - but no forum.
Given the cost of good forum software, and what webmasters and designers want to charge for a custom job, I thought the idea of a shared solution would work. Plus you get the benefit of cross-over from shared interests.
The advantage of going the blog route is it is a nice way to "get your feet wet" before shooting for a full blown CMS.
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