A large part of my job is about keeping up my knowledge of what is happening in media, technology and marketing. It's not enough to read all that's out there I need to make sure I have digested, understood and it put it context for myself. When I blog that's exactly what I'm doing.
My thoughts exactly. In fact, I'd go further: blogging has become my notebook and general repository of digital bits and bobs. Whenever I find something of interest (to me), I usually bung it up; I hope that it will be of interest to others, but that's really secondary. A blog is as much a very practical tool for my everyday work as an exercise in itself.