I've been meaning to add Eric Kaufman's Acephalous to the blogroll for some time. Here's a video of him talking about the pros and cons of academic blogging. But he also says something in passing about the importance of having a writing project that is not your dissertation. (If you've already written your dissertation, let's just take this as an argument for diversity in your writing portfolio. And specifically, of course, for blogging.) Here's my transcription of the passage. Most of this I could have said about my own blogging as well.
For the most part, my posts are actually long considered. I have a drafts folder. And that's one thing I can't speak highly enough of: it's constantly writing. Every night I sit down when I'm done working on my dissertation at 8:00 PM ... I sit down and write something that is absolutely not my dissertation. But I craft it. I actually work on my prose (my bold, Eric's italics). I don't just dash things off. I try very hard to write entertaining, funny, things, that are not my dissertation...
(Unlike the entertaining and funny things that are his dissertation, of course.)
Otherwise I would come, as I did actually before I started blogging, to hate writing. [Writing a dissertation] is a painful experience. And blogging is not.
Notice the regular pattern, the habit of writing that his craft implies.
Here's part two (about the Valve):