The issue here is how to determine if an anonymous guest has already rated or not.
When an authenticated user sets the rating, it is easy to determine if they have before or not and reflect the rating they've selected.
For an anonymous guest, you'd need some other sort of mechanism.
And it gets muddier depending on how to know if the rating being viewed is valid or not. If I'm a disgruntled user of your site and I figure out how to anonymously get 10,000 zero ratings in, you will undoubtedly show the item with a negative rating even if a valid 100 users say it's five-star. Likewise if I'm trying to artificially increase the rating and I can get 10,000 five stars in when actual users say it's a zero-star, the rating becomes invalid.
So, all things considered, I'm sure there's a way to do it (probably involving a hook of the jsp page and possibly some other changes), but it really begs the question is this something you want to do?
