Come on, this should be really easy to fix. If MailChimp is really sending you so many emails that you are upset with their service, you should be able to make your own MailChimp account and tell them that your email address requires double opt in. Or you can make a rule for their MX to end up in a special folder. Or they can detect a well above average number of lists for a single email address and trigger double opt-in for that address. This is a problem for a vast minority of users.
