Double opt-in, confirmed opt-in, email address verification, whatever you call it -- nobody ever universally agrees on whether or not you should do it. I see a lot of people in the anti-spam community try to recommend it based on their feelings. They relate specific experiences where a company annoyed them by not confirming subscriptions. Interesting, but it doesn’t always speak to senders in the language they need to hear. Unhappy anecdotes don’t provide the necessary info to convince marketers, who generally work by way of a data driven decision making process.