When I started writing this one, my intended audience was my family. It's evolved greatly along the way, and now my intended audience is much more inclusive. I write the most for my friends, but I also consider my family and colleagues in my posts. At the back of my mind I always think before making a public post: would I be willing to have a search committee twenty years from now read this post?
(I've been thinking a great deal about the social structures which work with writing this week. I haven't played with the poll function on LiveJournal before, but I'm slowly mentally designing one on the subject of writing and audience which I won't figure out or post until I'm no longer paying by the minute for almost-local dialup.)