I found out recently that unless you collect your mailing list addresses using this feature, sites such as the popular Mailchimp will reject your list.
Over the years I've spent attending book events, speaking to groups, and holding book signings, I collected many email addresses as people would hand me a card or write them out in our face-to-face contact. When I loaded this carefully-acquired list into a campaign I intended to promote the newly released Not Bound By Blood ( http://amzn.to/1V4OKQx,) Mailchimp disabled my account because it violated its requirements.
It's taken a couple days of digging on my part to correct the situation. First I had to own a domain name and create an email address at that site. Then I had to add an 'opt-in' button to my blog page. Only those addresses from contacts who click the 'opt-in' button and agree to receive future correspondence from me will be admissable to include in a future campaign or mass mailing through Mailchimp.
Consequently, all the time and effort I spent gathering email addresses in the past was wasted effort.
The whole situation reminds me of a form of entertainment I recently discovered available on the computer thanks to friend, Becca Anderson. She introduced me to a site that features jigsaw puzzles. I think I have all the pieces of this puzzle of using Mailchimp - just need to put the pieces together.
One last caveat: read the instructions first. Oh yeah, I'd appreciate if you'd submit your email at the top of the page...and add a comment...I love comments!