I agree that Library 2.0 is a very real and relevant force. I am concerned with the lack of authority within postings of wiki's and the like. Perhaps I'm old fashioned but other than getting and exchanging ideas and opinions, I'm not sure that many people have the expertise needed to contribute their text to authoritative documents. How do we contain users to appropriate context? How do we teach youngsters to use citations and relevant sources?
Just a couple of concerns.
I too think the amount of time spent exploring and joining groups is overwhelming. Although many of these tools may be greatly useful, you do have to select those which are most beneficial to you. We all gravitate towards our interests. It is fun to learn new items and at least have some background knowledge of what everyone is "talking" about.
On to thing 3.