That is my understanding of the CAN-SPAM act. You can only send transactional/relationship emails with prior agreement, And the only way to reliably verify that you have such agreement is through a user-initiated confirmation.

I am not a legal advisor, so prefer to Stay on the safe side here. Like I said, the feature is developed in v11 and webmasters should use it only when it is appropriate.

To give you a typical example - we built a site for an event venue, the venue collects patrons emails on paper. The site webmaster adds emails to database and believes that since emails were expressly given it is OK to confirm them manually. That is of course incorrect, because there is no way to know if these emails indeed belong to the patrons, if they indeed still want to receive emails or if there were any spelling errors. All emails have to be confirmed by users.