I believe the reasons Web 2.0 become what it is now, are neither share-by-default policies that most sites are following so religiously, nor the development of programming languages and frameworks, and absolutely not tagging and flashy colors.
The most important reason of the success of Web 2.0—and I’m still reluctant to use the term—is that its primary consumers aren’t those using our software, but those building upon it.
Programmers, coders, or developers are treated as first-class customer now, rather than antisocial, basement inhabitants. We’ve realizes that decisions are held in their hands, and that the masses of information can only be of little value unless opened for public consumption.
Unlike a mere five years ago, no self-respecting, Web-based start-up advertises its applications without backing it with extensive documentation. I don’t mean those, now archaic, Help pages (since no self-respecting, Web-based application should require explanation), but extensive documentation for developers to extract data, reform it, and re-serve it.
Re-serve, not reserve, is what makes Web 2.0.