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.

Well... this is not as much about hiding your address as it is about making sure that you don't get spammed much later after registering for a site.

Still: I am not logging alias resolution. The SMTP-Server is not logging a thing. Insofar, if authorities would ask me to give them data, I plain couldn't if the alias has expired by then.

If the alias is still valid, then of course, I would have to comply, but see my first point.