We see something else going on here. We have seen this problem for 1 user for months now. Of course, it is the owner of the company - and he is ready to kill someone over this. (me for starters). Single email account setup on this device. Exchange/Office365. No iCloud (Except findmyiPhone), no other accounts..
It appears to occur when using the contact 'search' funtion in the contact app or phone app on the iphone (or ipad, I believe)
1) User uses contact search funtion by typing text into the search field This works most of the time.
2) Periodically, the search function sort of locks up - and instantly - the phone starts downloading - what looks like and entirely new set of duplicate contacts from the server.
3) Duplicates are not created on the server (so far). They appear on the mobile device only.
4) Disabling the account on the phone, or simply turning off contacts and 'deleting' them on the phone and then turning contact sync on again resolves it temporarily. When the search function crashes again, the same thing (dupes/trips) happens again.
5) deleting the device and adding the account from Office365 and removing the accont on the iphone and setting it up again of course fixes it temporarily. When the problem is encountered within the contact search function again... the same thing happens. again.
We have wiped the phone before and it again fixes it temporarily. The contact search function - seems to me.. can trigger this at any time.
1900 contacts or so for this user, in a couple different 'groups'. I thought groups may have something to do with it (including 'suggested contacts' from Outlook 2010) but I am not convinced of this. It is almost like the contact app is having a soft crash (not closing)... getting confused... and assumes it needs to re-download everything at some points... and it is triggered by searchng contacts. Not 'almost'.. I have watched this happen while using the device: as you are searching the phone suddenly starts downloading all contacts a seccond time. Seaching contact from within the phone app, or seaching for contacts withing the contacts app.
We may wipe the phone again today, but I am pretty sure this does not fix it. I am beginning to suspect that it is a contact sync problem triggered by searching on the device - which somehow breaks or fails or errors out. Removing/Re-adding the device from 'office365' really does not remedy it either.. besides seeming to be a temporary fix until it suddenly breaks again.
I believe it happens on the iPad too, which is wierd because it seems to me the ipad contact app is very different... but perhaps the 'searching' and 'contact sync' functions are the same.
can anyone confirm this behavior?
(note: http://community.office365.com/en-us/f/160/p/18512/196489.aspx#196489 )