Well, yes, in some ways. I find that it takes me at least an hour each morning to read my email and write the blog. Is that a bad thing? I don't know.
What I get from blogging is hard to define. Of course I get responses sometimes, and that's fun because I get to "know" people who react to a topic I've chosen. But the real benefit is more personal, and I can only liken it to the journal-keeping of earlier centuries. Many, many people kept journals in the days before computers, and I'm sure at times they wondered if all that writing was time well spent or time wasted. I'd like to argue for the former.
First, on a personal level: writing down my thoughts helps me understand how I think and how I write. Going back over it later can reveal holes in my writing style, enabling me to improve. Second, blogging solidifies in my mind what's important to me. Over time, I see themes that reveal where my mind likes to be. Third, it lets me see, as I go back over the accumlated writing, how I've changed (hopefully grown) over time.
As far as the rest of the world goes, blogging acquaints me with others and possibly garners interest in me as a writer. I'm sure it categorizes me, but that's not bad, since I'd rather people come to my work knowing what they're getting.
If we face facts, most bloggers know that they reach a tiny, tiny audience. I blog for them of course, hoping that they enjoy the day's notations. But mostly, I have to admit, I blog for myself.