Not so keen on that sig - it sounds very harsh 'if you don't like these emails, we can always delete your account from our site!'
Would be much better to include a link to unsubscribe the user from the notices - obviously it would be a different link for each type of notice.
Most of these options, like watched threads, can be turned off and on by the user, so we really want to have a system whereby they know how to do it themselves rather than burdening the admin with it all
