Eurobrat has a good post about blogging. Read it, and be sure to read the comments as well. (Although I take issue with her computer game comments. (J/K))
Ultimately, she comes to the same conclusion I have, which is that blogging is worth doing even if no one reads it. I read a good article about this long ago, back when almost nobody read my blog. The advice the author gives is spot-on from my experience–writing this blog has helped me think better and more clearly about all kinds of issues. (And I have acquired a few more readers since since I read that article!)
There really is nothing like blogging for helping you think.