Example use case:
1. Get frustrated with MS lookOut for the last time,
import calendar and contact list from Outlook into Thunderbird and Lightning 
2. Install BirdieSync and use for about 3 weeks
3. Discover that ActiveSync will allow direct syncup with an Microsoft Exchange server
4. Lose brain, think, "That might be a really good idea."
5. Discover that Open-Xchange is not close enough to Microsoft Exchange to make that work
6. Delete the Microsoft Exchange account in the Windows PC's ActiveSync client
7. Try to make phone call from WM6.0 phone using voice recognition, "call by name," phone says "what are you talking about?"
8. Panic when you discover that all of your Contacts are gone (though Calendar oddly intact)
9. Panic when you discover that all of your Contacts are gone from Thunderbird too
10. --> This is where that feature comes in <--
Alternate #10 possible because of #1:
Re-import from Outlook and pray that you didn't change anything important in your Address Book since the time of the import. 11. Cardiac arrest averted.
Thanks!!