Emergency Medicine News had a recent article looking at the growing trend of physician bloggers.
While some bloggers have been able to monetize their sites, most simply write for fun. Physicians who blog must be especially careful to protect their patients' privacy if clinical cases are discussed, and physicians must realize that things written on the internet are permanent.
KevinMD.com had a recent post discussing the importance of a physician's online reputation. Blogging can be a useful tool for both physician and patient, but needs to be realized as a potential risk as well as benefit.
If you want to know more about your own reputation online, Joy Tu of Medical Justice wrote this excellent post on influencing your online reputation.