The struggle continues - why blog?

I keep struggling to understand why I am motivated to maintain blogs. Is it solely narcissism at work? This is likely part of the explanation. I heard a quote regarding the Internet 2.0 phenomenon. The Web 2.0 focuses on virtual communities, social networking, decentralization of content creation. Web 2.0 includes technologies and services, such as Flikr, MySpace, Facebook, blogging, YouTube, etc. The paraphrased quote is "Andy Warhol, when describing the pop culture phenomenon of the 60's and 70's said 'Everyone will have 15 minutes of fame' with Web 2.0 everyone will be famous to 15 people".
However, a recent project in which I was asked to write and communicate requirements for a financial trading system convinced me my writing and communication skills had atrophied. Not only this, I am not sure my communication was that precise before aging and inactivity eroded my skills further. I don't recall ever thoroughly analyzing the quality of my communication.
So what does this have to do with blogging?
I realized that when you write something for publication, there is more pressure on refining one's thoughts and checking one's facts. So for me blogging is a very good way to share information that is valuable to me, while at the same time giving me a medium where I can practice improving the precision and quality of my writing. There is an old saying, "If you want to learn something, teach it". My use of blogging to help communicate what I think I know is proving to be a great way to organize my thoughts and improve my communication skills.
Do I have an example of blogging helping to improve my own quality?
Why yes, just today I was writing a blog entry on a useful software program I use to merge and split PDF documents. Initially I wrote about the value of low cost PDF utilities as compared with the licensing cost of Adobe Acrobat Exchange. The question the blog entry created for me was, is the total cost of a set of single use utilities really cost effective when compared to acquiring an integrated product, such as Adobe Acrobat Professional? To my surprise, it may not be the case, as Adobe has added functionality to Professional and also reduced the license fee. I likely would not have corrected my incorrect assumptions had it not been for the motivation to share information regarding a program I found useful for my business.