The results of the Blogging Common survey, which many of us participated in earlier in the year, can be found here. Interesting stuff, if not particularly surprising. One of their more notable results, perhaps, is this:
Typical bloggers spend a third of their blogs writing about their personal lives; highly linked to bloggers tend to share commentary and opinion.
On average, “diary and personal experience” makes up 36% of the content on blogs written by English-language bloggers. Popular bloggers spend only 18% of their blogs writing about their personal lives and 48% on commentary and opinion.
I was interviewed as part of their pool of "popular" bloggers and I will note that I hardly ever write about myself per se, under the assumption that this would bore readers.
A 2nd notable survey result is that, among "highly linked-to" bloggers, the single most popular posting topic is Politics. I suppose that's not surprising either; writing/reading about politics doesn't require a great degree of specialized knowledge-- its actually fairly difficult to have your views proven definitively wrong--and so while everyone has an opinion, nobody is afraid to weigh in with it.