Google Takeout is an invaluable tool to store a copy of your Google Account data or to transfer to a new account. Sadly, for no reasons specified, the ability to transfer your Google+ circles & connections will be removed starting December 4th.
"Starting December 4, circle and connection transfers won't be available anymore. We're sorry for the inconvenience." - Google+ Help Centre
To be fair, this won't affect that many of us, and you'll still be able to download a copy to Drive or a variety of other ways. It just means that we have one less way to handle our circles data come early December.
For more information, make sure to check out the Google+ Help Centre for circle & connections account transfers.