Seth Godin asked the question If no one reads your blog, does it exist? He said simply writing a blog forces the author to be "respectful and clear" which is important.
Yes, if you write a blog and no one reads it, it exists, BUT it exists in a horrible unfulfilling state. The point of writing, of communicating is to reach someone else, to connect. If you put a message in a bottle and toss it into the ocean (a lot like the feeling you get when you post the first entry in a new blog), what you want is for someone on a distant shore to find the bottle and message and READ IT. What you really hope is that they contact you back and you get the joy of knowing that you connected and communicated. That's the thrill of writing.
I would argue that most blogs die, not from lack of the blog writer posting, but from a lack of comments. A blog is meant to be chatty and it's hard to chat by yourself. And if you do chat to yourself easily, it's hard to feel that it's particularly worthwhile.
Wow, I just came up with a new service. The I'll-comment-on-your-blog service. Anyone out there who is feeling that their blog is dieing (dying?) a slow death from lack of feedback, can (hmm... should I charge a fee?) request a comment on their blog. And I'll make it a meaningful, discussion-inviting comment too (ok, it might have a misspelling or two).
A blog without readers, without commenters, is like a person on life-support. Sadly, it's just usually a matter of time.