I agree with clocktower ... I have clients that I shoot for that could subscribe to a gallery and as photos are added, maybe just once a day, they get an email saying items were added to gallery, much like box.net does now. It would save a great deal of time uploading, then pulling up client email addresses, composing emails, then sending them out.
Vin, the customer is subscribing, so the email verification is not needed. They are not gaining content, just being notified of content. If they don't want the email, they just don't subscribe.