My two cents worth: If somebody wants to rate (and review) a story then it really isn't a hardship for them to be registered. Using a hotmail style email addr means the person can be as anonymous as they want to be.
Besides, I like the feature that lists a reviewer's 'history'. It gives an idea about whether to trust a review. This would be lost if the site returned to unregistered reviewing.
Faibhar, I'm impressed by your relaxed attitude to reviews. I assumed a prime motivator for posting on this site is for the reviews and feedback. Even though it seems a paltry amount in comparison to the actual downloads.