"Web 2.0" may be the most used and abused buzz term on the Web.
People made fortunes with conference around it, consulting on it and using the template to duplicate it with any domain like "Bank 2.0", "Supply Chain 2.0", "IT 2.0" or whatever.
To agree, I think we CAN recognize that a series of evolutions in the way people use the Web can be synthetized with a concept.
But I will refer more to waves, illustrating the fact that these evolutions are not perfectly synchronized and exhibit a certain kind of fuzziness which let the smartest entrepreneurs profit from their prime understanding.
For me, one of the key characteristics of the Web and of computers in general is the trend towards massification. Habits, usages and skills that were previously limited are massively made available to the greatest.
Let me sum up the first two waves regarding this axis : this will lead to what I think will characterize the third one.

1) The First Wave Of The Web was about Mass Consumption

Turning back to the 90s, the Web for most of the users were primarly about "consumption" of information, made massively available by the low cost of publication through easier programming languages, free web server and cheap bandwidth.
People were able to access a big flow of information coming from anywhere in the world.
Tools like Google Search allowed us to find what we want to know.
People were the primary requesters of information and the main consumers of it.
Production were still a professional activity and most seen websites were so digital copy of the traditional media machines.

2) The Second Wave Of The Web is about Mass Production

Since the 2000s, the Web for more and more users is also about "production" of information, made massively available by easy to use tools as blogs, wikis, etc...
Now (almost) anyone can produce a text, image, sound or video, make it available for anyone else to consume.
People are also commenting media, rate it, like it, forward it.
In this framework, Facebook is a good example of the latest incarnation of it, centralizing every media you produce in a single place, and organizing it around you as a person.

3) The Third Wave Of The Web will be about Mass Delegation

So after consumption and production what will we need, to constitute the Third Wave ?
I sum up this by the term "Mass Delegation" : the need not to just use computers for me to do things but also to do things FOR me.
In a world, where there is 2000 years of video on YouTube, 2 billion people on the Web and 200 to 300 people gravitating around me, I will need a computer to which DELEGATE many tasks in order to cope with the scale at which the Web has evolved, for example :

Remember for me what, where, when and why I did see, read, hear, make, write, like.
Buy or book for me.
Tell the people I want in my name about me.
Suggest for me what I will want to see, read, hear, do.

Thus, the next wave of the web will be about the need of digital proxy, more and more useful as it knows about me.
And there will be two ways to get it.
The first will be centralized, massive failure prone, privacy challenging, advertising loaded, aka Facebook.
The second will be personal, intimate, controlled, aka...?