My yesterday's posting prompted my dear friend Raj Shekhar to lend his precious comments. It was then he noticed that I didn't had Anonymous posts allowed on my blog. And when he told me about it on MSN I thought that it was probably that the default setting was blocking anonymous postings.
Funny thing I spent more than an hour and couldn't find a solution. So I turned to the forums at Community Server, unfortunately I couldn't find anything that helped. Finally I was able to find this post by Sohaib Athar which solved the problem for me. I think I'm gonna make a post into the CS forums for people who are also facing this problem.