Don't focus on the single post. Rather a good blog provides you a whole vision of what a field is about, what the interesting questions are, and how you might answer them. It is also a new window onto a mind. And by packaging intellectual content with some personality, bloggers appeal to the biological instincts of blog readers. Be as intellectual as you want, you still are programmed to find people more memorable than ideas. The academic blogger faces the new challenge of tying these disparate functions together in a compelling product. Intellectual substance, personality, writing, and editing, that is our juggling act.
This hypothesis suggests, by the way, that reading a blog many times will be more rewarding than just sampling it once. Readers should "specialize" their blog reading to some degree, rather than jumping around and reading the best posts on a given day.