I began reading blogs long before I gathered the momentum to start my own. In the beginning I did not understand the unwritten rules of blogging and commenting. I thought that commenting on a blog was akin to asking a question in the middle of a university lecture i.e. something one should only do if they have read all of the material and in general come to class prepared, otherwise it is a waste of everyone's time. Then I began to realize that comments were generally welcome and did not necessarily have to be earthshatteringly insightful.
I started my own blog without completely understanding why I was doing so. Since then I have pondered why people blog and, indeed, why I myself have started. I think it boils down to the following-
Sharing the wealth
I think some people genuinely feel they have a wealth of knowledge to share and some genuinely do. Blogging to them is a form of sharing this wealth among their readers.
Seeking and offering support
The first blogs I read were those of people struggling with infertility. The network of support among these bloggers was amazing to me. Clearly these people (mostly women) draw strength from each other and blogging is a form of cheap therapy. I imagine this is the case for many other communities of people struggling with various issues.
There is something fundamentally human in seeking others who share common experience. People out there in the void who can, in some way, relate to our path in this life. I guess I was seeking and have found a community of runners, mommies and running mommies.
In the real world one must so often shout to be heard, a blog gives one a soapbox on which to preach one's deeepest held beliefs without interruption. In one's blog, one is master of the castle, one gets the first and last word. There is something very powerful about that.
Exercising the literary muscles
I have the feeling that deep down inside EVERYBODY supposes they'll eventually write a book someday. I have a friend here whose job it is to screen unsolicited manuscripts that are sent into her publishing company and she assures me that the VAST majority of people should NOT. Regardless blogging is a great way to flex the creative muscles and practice a very basic form of self expression; something that most people don't do once they are out of formal schooling.
Quest for accountability
Many people seem to start blogs when they are attempting to make an overwhelming, positive change in their life - losing weight, training for a marathon, quiting bad habit X, Y and Z. I think blogging about it gives them a feeling of accountability to the unknown audience and helps to keep them on track.
Recording one's history
Certainly a huge part of blogging has to be recording the passing of one's days. What did I do? Why was it important? What did I learn? What do I look forward to? What do I regret? A blog is basically a diary to may people, a way of making sure that what has passed will not be forgotten. But of course if the major motivation were simply to record one's history, there would be no need to broadcast it to the world which leads me to the last, and most primal reason for blogging...
I think fundamentally many people blog as a way to shout to a vast and largely indifferent universe: I'M ALIVE! What I do matters! I was here and I did something with my life... Call it narcissistic, call it self-absorbed. I think it is deeply and fundamentally human.