Many early adopters of Twitter are undoubtedly horrified that the arbiter of all things mainstream, Time magazine, has published a cover story about the social networking site.   Let them complain that Twitter is no longer cool.  The rest of us know that it’s an invaluable means of communication and an excellent barometer of public sentiment.  Sure, there are always cooler things around the corner.  And it’s entirely possible that some will be even bigger and better than Twitter. Until then, Tweet away.