The crux of the privacy concern is that it doesn't matter what you write on your privacy page as people have no way to make sure you live up to it. If I wanted an email address that couldn't be traced to me, then this sort of service will never suffice. Then again I don't imagine that is your target market or intended use.

edit: I just want to add that I think it looks really useful for all those cases when privacy is a lesser concern, and I've bookmarked the site for future use.