All the major companies use confirmed opt in and I certainly recommend you doing the same thing, don't be so concerned with the size of your email list and ignore the quality. You want to use confirmed opt-in email so that you know all your recipients of your email want to be on your list. (unsubscribe link on every email)
Most people have accepted the fact that you have to confirm email all the time for many different reasons and have grown accustomed to it. If your thank you page is clear and you feel it's as reasonable as you can make it, well then, forget the people who drop out and lower your confirmation rate. Concentrate on getting new subscribers and don't be too self conscious about your confirmation rate.
One problem you may want to address though is the word "subscribe", that word has some negative connotations in some people s' mind right away. This can be overcome if your opt-in email advertising reiterates to your potential subscriber that your newsletter or whatever the case may be is FREE.
Many programs allow for you to have a lot of control over the templates and the verbage that goes with it. Do tests and find out what works best for you. I personally don't see any negatives associated with the word "subscribe", but hey, we're all different.
How often you send out offers to your list is a whole matter altogether, just simply ask yourself when you've unsubscribed to someone before and why you did it. If your opt in email advertising is too strong, well, believe me, you'll soon find out.
Once you've mastered your opt-n email advertising then your business will see some great results.
About the AuthorBusinessman/ entrepreneur and freelance writer interested in politics, marketing, sports, and personal development http://best-email-marketing-service.com