I was using the Anonymous Blog Comments from codeplex, when I added the anonymousblog.webpart and submited my comments for a blog it threw this error:
"BLOG ID is missing".
I realized that I added the anonymousblog.web part to the main blog page and not the actual post. Basically we need to add this web-part to the actual blog post, click on the blog-post to view one of the posts on your blog site, and replace the out of the box Comment web part with the anonymous web part. Now try submitting your comment it should work.