Siri and shared contacts (1 MobileMe on two phones)

['73-B]

I searched around but didn't find anything on this, so I'm wondering if anyone else has run into this. Me and my wife share a MobileMe (now iCloud) account which is also our iTunes account. We both got the 4s, but I'm running into an issue with Siri not referring to one person or the other correctly. If I set our names in the My Info field under the Siri settings and then enable contact list for the iCloud account one phone will suddenly change the My Info to the other person's name. Just wondering if anyone has run into this and if there is a way around this or if we need to just break up our contact lists and use two iCloud accounts.