This is a good post to follow the previous one. About 3 years ago, I switched my focus from Web 1.0 to Web 2.o and 3.0 research. Of course, the words don't matter - the hype around using version numbers is kind of silly. But the basic idea (at least as I define it) is that in Web 2.0, things are more interactive (using Ajax etc.) and allow users to contribute (upload content, tag content, respond to content, etc). Web 3.0 takes it up a level, with semantic analysis that helps to organize all the masses of content out there. Web 2.0 + Semantic Web = Web 3.0.
Right now, most social networking is Web 2.0. Anyone can add content (with some filters and restrictions), but finding what you want relies on older search tools (no offense Google). I suspect it will only be a few years until we have real Web 3.0 social networks to use.
So it was interesting to see Google announce its sort-of rival to Wikipedia. Knol (I am not sure who drummed up that name) is also an on-line encyclopedia-type resource, but instead of a wiki, users upload their articles as units, each one associated with the bio of the author. They are not editable by others. So readers get a sense of how much they can trust the content based on the credentials of the author. Readers can also rank each article and higher ranked articles will bubble to the top. Google added reputation management but removed the "wisdom of crowds."
It will take a while for Knol to catch up to Wikipedia in the amount of content. Until then, it is impossible to compare the approaches. But when (if) it does, it will be interesting to see the difference. I am sure there will advantages and disadvantages of each one.