I have a user who is complaining of this weird problem.

She has an iPhone w/ exchange mail/contacts/calendar sync configured. If the exchange server goes down briefly, she immediately has no contacts available on the phone. They're all gone.

Contacts normally return when the server comes back up. However, this user cannot apparently tolerate being without mobile phone contacts for even 5 minutes.

Is there some way to keep this from happening? If we could cache the contacts in an "offline" fashion on the phone, that'd be awesome. Also a concern is that we would want to avoid any method that may result in duplicate contacts.