Why is dot com 2.0 happening? Technological discontinuity takes some time - because the dominant design for many innovations is still waiting to be discovered: BigString, for example, now offers erasable-recallable email. Or because those that have discovered something close to a dominant design have created massive new niches - like Amazon's done with it's (lame) attempts at price discrimination, paving the way for Pricenoia, which compares Amazon prices across markets. Or because shifts in regulation shift the value equation: Adnoodle wants to let consumers auction their privacy from direct marketers, driven by do-not-call/spam laws.
Will any of these succeed? Forget about that - ask yourself what the value equation is going to be, and how the dominant design must answer it.