I posted this as a Cosmic Variance comment, I've revised it a bit here ...
.. There's a meme about “commodity bloggers” and “echo chambers” that’s been simmering for a while but was fired up by a recent Jakob Nielsen post. CH has a good overview.
I think this is a sub-meme of the “blogging” is “destroying all that is good and pure and noble in human civilization” usually alternating with the “wikipedia is destroying education” meme. (More on the latter soon, maybe...)
Beyond these memes is an unspoken wariness about the increasingly subtle distinctions between an “echo chamber” blog and a splog — the more sophisticated splogs are eerily similar to low end commodity blogs.
I’ve nothing else to add to the good comments on the CV thread, save perhaps that my own very low readership blogs are written for these audiences in this order:
1. Myself. It’s how I learn and think.
2. The GoogleMind: building inferential links for search and reflection.
3. Tech blog: Future readers who find my posts useful to solve a problem they have that I've solved for myself.
4. Gordon's Notes: My grandchildren, so I can say I didn't remain silent -- and my tiny audience of regular readers, not least my wife (hey, we don't get that much time to talk!).
I, of course, agree with the obvious consensus that blogs are intended to be read by subscription tools (like bloglines) and that descriptive titles and label/categories should allow readers lots of tools to decide what to read. I do think the readers can, and will, make better use of metadata (themes, categories, labels, etc) in years to come.
Update: I revised my "why I write" list as I thought it over a bit more.
Update 7/17/07: Excellent comments by Rosenberg. For love, not money.