James links to this discussion on why academics blog. Some excellent questions are posed...with great responses. A few quick responses from my own perspective:
Why do you blog? To work through ideas...to create a history/record of my thoughts and their evolution. To find a pattern in the rapid flow of information.
What keeps you going?Same reasons as why I started...With the added benefit of being involved in a community of people that I dialogue with indirectly (i.e. I speak to them through my blog, I listen to them through theirs. I've largely given up on blog comments as dialogue. Time for revised expectations...:)).
What do you get from reading other blogs? Diversity of opinion...clash of ideas...synthesis...more complete perspective of issues...discovery of new trends before they become mainstream.