Verifying email addresses is vitally important for building a high quality list. Otherwise, you can easily sign up other people for the list, they get essential

Verifying email addresses is vitally important for building a high quality list. Otherwise, you can easily sign up other people for the list, they get essentially a spam email, report it as spam, and all of a sudden your list is crap because they didn't have double opt-in. Keep double opt-in, it's necessary (and I think required in Mailchimp's case unless you use the API directly).