I agree that votes should be kept anonymous. However, it would be nice to be able to notify voters of changes, particularly down-voters.
For example, say a new user posts a question that's unfortunately worded and appears very off topic. That question would likely be down-voted. Then, later, the question may be updated to fit within the guidelines of the site. However, the down-votes remain.
It would be nice to be able to notify the down-voters of that situation. Perhaps via a comment tag "@Downvoters Please check my edits and see if your downvote is still warranted, thanks". The down-votes are for the question after all, not the user. So when the question is altered, shouldn't it get a chance at being reconsidered?
It has the additional benefit of allowing for clarification. It's unfortunate when I see a post with 2+ down-votes and no comments, especially when the reason for the down-votes might not be obvious to the OP. So someone can say "@Downvoters, can you please comment on why you're down-voting so I can improve the question/answer?"
I suppose we'd have to try it out to see if that creates too much notification spam.
While this does have the potential for abuse (giving angry people a way to yell at down-voters) I think that can be controlled the same way any other uncivil comment is dealt with (and likely more swiftly since people will be alerted to it!).