The Community College Dean has written about why he blogs, and asks any and all readers to tack on to his effort.
My blog is not very anonymous. It is occasionally personal, occasionally political and throughout a venting location for thoughts, and a place where I formulate myself in higher detail - so to speak a scratchpad, but public enough for me to allow others to read it.
I write it to formulate my own thoughts further, find possible errors, start discussions, or just jot down the viewpoints that illuminated some point of some argument for me. I do it in public because I thouroughly enjoy the conversations it sparks.
I can see the charm of anonymity, but I am way too much of an attention junkie to be able to stay anonymous for very long. This has come up in my career - thoughts about job applications in process, published on this blog, and even more on my livejournal, sparked questions at the hiring interview with the potential (and now current) employer about my writings and what influence the there formulated ideas would have on my actual poise toward my current job.