Here's how it works as I understand the process. What I am doing is placing all of my contacts in the shared address book, as such making it available to all of the various identities I have configured on this system.

My plan is to keep the individual address books empty so when I wish to backup my contact list there is only a single address book file to worry about. Here's how that's accomplished.

1 Open up your address book and focus on the current identities contact list.
2 Select all of the contacts listed there and copy them to the clipboard.
3 Tab one time and arrow up to shared contacts.
4 Tab over twice to the listing and paste the contents of your clipboard right there.
5 You will need to hit enter on every entry that is being pasted in the new location, kind of like an approval process sort of thing.

The export process is as follows:

1 Open up the address book in what ever identity you happen to be in at the time. In my case it doesn't matter since everything is now going in to shared contacts.
2 Tab over until you hear the name of the current identities address book and arrow up one time to shared.
3 Open up the file menu and pick export.
4 Hit enter on the first choice which is WAB files.
5 Give your backup a name for example address book.
6 Hit enter and follow the prompts.
You're done.

Restoring is done as follows:I must point out it's a little tricky so pay close attention please.

1 Open up your address book with control+shift+b.
2 It doesn't matter if you're focused on shared contacts or not because when ever you import an address book file it seems to always go in the current identities' contact list. So open up the file menu and hit import.
3 Hit enter on WAB file and browse to select your file of choice.
4 Finish the import process which uses a standard dialog box interface.
You're done.