I agree that it is not a "platform" but it does provide real-time news and discussion like no other tool at this time.
Obviously, people who Tweet that they are riding the train to work don't 'get it.'
But those of us who have formed discussion groups using hashtags do.
As an example, I'm CulinaryHatchet, have a blog (that I've been neglecting while working on BHeardusa.com start-up), really into the #profood movement and have met many other very informed #profood -ies (as well as #agchat and #foodinc) on Twitter, including the son of the people from whom Michael Pollan (Omnivore's Dilemma) purchased his cow. There is great discussion in #profood from all sides of the issue. There are farmers, farmer's markets, attorneys, journalists, restaurants, etc. I can't think of any other resource that provides this kind of value right this second (although BHeardUSA.com will be taking it to the next level and using Twitter as one of the tools.)