If you aren't, you probably should be! If you're not convinced, read Joel Oleson's excellent post on why you should blog. To cut a long story short, through blogging we have collectively raised the bar in terms of available and accessible resources. As a result, it has made us all more productive.
IT professionals have for obvious reasons been the first to adapt and create an invaluable blogosphere of information and knowledge. However, this may start spreading rapidly into many other professions very very soon. There simply are too many benefits to be reaped to ignore it.
Still too many are reluctant to share because they feel they're giving away valuable IP. But the world is changing. IP is no longer the raw information itself. Your real IP is about how effectively you utilise the information and use it in new and innovative ways.
Blogging is only one of the many new tools changing the way we all work. Others include tools for social bookmarking, peer production, ideagoras, crowdsourcing and tons of other emerging concepts that will require practically any business to change radically to stay competitive. If you have an interest in Web 2.0 and the future of business I can recommend you read Wikinomics by Don Tapscott and Anthony D. Williams. It's a facinating read!