Here at Supernova 2002, listening to Smart Mobs author Howard Rheingold. (Good or bad, I heard him on Tech Nation last night, cover a lot of similar ground.)
Rheingold's vision of the future may require that people constantly express opinions in order to achieve a status among their peers or anonymous strangers. Won't people get tired of this? Look at reviews on Amazon.com. Look at Slashdot posts. Too much content overwhelms the ability to see anything but an abstract score, even when the best writing rises to the top. This means that your hard-written prose only gets read by a relatively few people, which eventually can make you cynical about contributing.
Pockets of community have to develop, but Rheingold talks about finding out the value of many resources through constant peer contribution, and I'm doubtful that the most likely to contribute will maintain their participation over time.