Liquid threads are kind of better, but still not ideal. My main concern is that this still requires you to go to different pages, some are difficult to get to (have to know it specifically or get refered). For example, if someone were to ask a question/start a discussion on certain type of targeting etc.
Personally I think a forum works the best, as it can break things down into different categories and list everything out in a manageable fashion.
The Facebook group is good, but it lacks the community involvement, in my opinion.
Google+ seems cool, but I can't sign up for it with my Google Apps account..
... and who uses yahoo? :P