My eXtension buddies claim blogging as something one should do because "everyone has something to say." To take that one step farther, I'll suggest that it allows a person some therapy from the "7 Habits of Highly Effective People." It does so by allowing one to vent about things in their circle of concern, while spending our productive time within our circle of influence. With a little luck, someone will read your posts who *does* have influence over things with which you are concerned.
Blogging is more about the writer than the reader. Much of the notion is exactly like a diary. No need to be defensive -- indeed the opportunity for learning does exist.