I was originally going to post this as a comment under the previous Web 3.0 entry. But, I thought it might get better visibility this way.
It's a bit esoteric, but here's an interesting article about visualizing Wiki contributions over time.
I can't find the original article that linked to it, but it mentioned that the "evolution" wiki is updated within 5 minutes of a defacement.
Speaking of user-generated content. A fellow I work with mentioned that in a recent meeting with top Silicon valley venture capitalists they outlined "user-generated content" as being one of the top 5 criteria that they currently use for deciding on ideas to fund.