Convert the circle data in Google+ to text for your backup.
You can backup your circle data (user list) in Google+ with this extension.
How to backup:
1. Mouse over to the upper-right corner as the screenshot1, and you will see a checkbox. (Screenshot1 and Screenshot2)
2. Check the checkbox, and you will see a control box. (Screenshot3)
3. Click "GetData" button, and your current circle data will be loaded in the text box in control box, as text. (Screenshot4)
4. Copy and save the text data for later use.
5. Click "close" in the upper-right corner of control box, and the box will be gone.
How to restore:
1. Follow 1 and 2 of backup procedure to show control box. (Screenshot1, Screenshot2, and Screenshot3)
2. Copy your saved circle data (text) into the text box in control box.
3. Click "ShowUserLinks" button, and you will see a user badge list below the button. (Screenshot5)
4. Now you can circle or anything you can do with the usual Google+ user badge.
NOTE: The circle data has what the circles each user in. But currently, the infomation is not displayed in the list because I'm wondering how should I show them in GUI point of view.