Update: It happened again, and this time I captured the message:
Can’t post for Adnans Sysadmin/dev blog because com.google.blogger.exceptions.RateLimitingException: For anti-spam verification purposes, please login to Blogger.com and create a post on your blog. You will need to solve a CAPTCHA.
Doesn't look like they have implemented it completely yet. I logged in to blogger, went to create a new post, and no CAPTCHA.
Update: Looks like they've finally implemented it this morning. But once I enter the CAPTCHA, and hit publish post, the web page keeps reloading, without actually publishing. Irritating.