I somewhat agree with you, but the research is skewed... then again what research isn't? Social media does allow for a lot of debate and it is quite active with people posting links and responding when it is an issue they are passionate about. This is so much the case that I've often hidden people to avoid being drawn into a lengthy back and forth on Facebook with people who are simply ranting and want to be heard, but are not open to a solid debate.
I think your best point is definitely the fact that it is fleeting. This is the problem with social media. It is lightning fast and continues moving along and conversations are eventually lost within a day or two as the next new "like" or "share" is posted. This is why I really liked your suggestions a while back in regard to using Disqus where your responses can be cataloged and supported with stats and you can build an audience through responding.
I think the message board is taking a hit primarily because people don't have the ability to write nuanced or informed long responses. This goes back to your "stupid" post as well. I'm definitely realizing the benefits of actively blogging in regard to building my writing career and with the addition of Disqus and my interaction on various websites, Spreecast, youtube, etc my site is indeed developing a nice amount of traffic. My decision to begin building reviews around my Amazon Associates account is also paying for a tank of gas each month.
I guess ultimately everything runs its course, and the message board is becoming a lost treasure. I do appreciate all of your efforts though and I am making a real effort to participate. I only wish others would do something similar. That would be the difference maker. Those who are already aware help, but there have to be new converts from lurkers to writers.
Is that a call to arms? Yep... come on lurkers share the page on your blogs and let's rebuild those web chains from the 90s.