I've been getting a lot of spam comments on the blog so I added a CAPTCHA to comment posting. Specifically, I have added CAPTCHA's from the reCAPTCHA project which uses CAPTCHA's to help digitize old books. Adding the CAPTCHA's was greatly facilitated by the WordPress reCAPTCHA plugin. So rest assured, every time you post a comment, you are helping to enlarge the freely available intellectual commons.