Why "Web 2.0" is a great name for Web 2.0
I have a much simpler take on the subject. Web 1.0 is the 1-way use of the Web, and Web 2.0 is the 2-way use of the Web.
The Web holds “content”. Content is put there by someone, a producer, and used by someone, a consumer. Web 1.0 applications have a few producers (usually called publishers) and lots of consumers (usually called users), just like in traditional media such as newspapers and television. And they are separate groups of people. In Web 2.0 applications, people can be both producers and consumers (the term “prosumer” is sometimes used for this). Ebay may have been around for quite a while, but it’s a Web 2.0 application: most content comes from the users. Amazon is more typical of a Web 1.0 application, with a one-way flow from Amazon and its partners to the users. Amazon did, however, have a Web 2.0 characteristic early on, by including user-contributed reviews, and later also added the ability for users to sell their own items alongside those for sale by Amazon itself. So one might say that Amazon’s been upgrading from 1.0 to 2.0.
Notice how I referred to “Web 1.0 applications” and “Web 2.0 applications”. The Web hasn't changed; what has happened is the advent of various new applications that use the Web differently from most earlier applications. The Web now contains both 1.0 and 2.0 applications.
I’m not the first to say that Web 1.0 is the 1-way Web and Web 2.0 is the 2-way Web, and I’m puzzled that this view isn’t more common. It might be partly because the term “2-way Web” has for at least five years been used to refer to something else, namely the use of HTTP to push information to other places on the Web, not just to pull information into a browser window.
So what about those other commonly mentioned characteristics of Web 2.0? Tim O’Reilly lists fourteen examples of 1.0 vs. 2.0 uses of the Web, such as Akamai vs. BitTorrent and page views vs. cost per click. Most of them clearly fit the 1-way vs. 2-way model (including the two examples I just mentioned). He then goes on to identify seven principles: The Web as Platform, Harnessing Collective Intelligence, Data is the Next Intel Inside, End of the Software Release Cycle, Lightweight Programming Models, Software Above the Level of a Single Device, and Rich User Experiences. Well, that’s all great stuff, but a useful definition of anything can’t be five pages long. If anyone really wants me to, I can go into each of those seven principles and argue how it either fits the 1-way vs. 2-way model or should be dropped as a Web 2.0 principle.
I do however want to mention Ajax (a technique for letting users cause the page in front of them to be modified without a whole page refresh). Yes, sites that use Ajax tend to be called Web 2.0 sites. But think about it: in the 1-way Web, does a user need to modify the page? Not too often (generally only for things like zoom in/out). In the 2-way Web the user may be a producer and is far more likely to benefit from dynamic page changes in response to input coming from the user side. This role of the user as an active participant, and not merely as a reader in Web 1.0, also makes things like a larger font more important. My complaints during the dot-com era about tiny fonts that made pages look cool but couldn’t be read by anyone over 40 have largely gone away, thanks not to any increase in good sense on the part of web designers but thanks largely to Web 2.0 applications that require user interaction with the pages. For that reason alone I personally am grateful to Web 2.0. So what if it'll also cause deflation, unemployment, ... but that's a topic for another post.