A blog is the “unedited voice of a person”:
The lack of editing is central, because it’s one person who’s responsible for every word. When you click the Publish button you should feel butterflies, at least sometimes, because there’s no one to pass the buck to. If someone else wrote the headline, or did a copy edit, or even reviewed what you wrote and critiqued it before it went out, it’s still writing, but it is not a blog.
I’ve written my own thoughts, long ago, on “definitions” of blog, blogging, bloggers, but I very much like Dave Winer’s “unedited voice” idea which is becoming more of an important distinction when everything can “look” or even “feel” like a blog.
Or, maybe it’s just semantics. Is it all just writing?
I’ll keep calling it a blog. It’ll always be that way for me.