Same here. And I agree that it has to do with the iCloud sync.
I have also two iPhone 4S and when I set up my wife's yesterday I found out that it seems to sync 'My Info' across both phones. This is very annoying speciall when you tend to use Siri a lot. I mean Siri is gonna call both of us either with my name or my wife's (depending on what we leave the My Info at).
Or when one of us says 'call my husband/wife' Siri won't be able to know who to call. I just tested that, not knowing that it was synced to my wifes name. I said 'call my wife' and Siri started asking which phone number (it was all set up previously)... and then when I decided on the iPhone number I realised that Siri is actually calling me (the husband)... as I had it set up on my wife's phone just last night.
I know Siri is in Beta, but Apple, can you please make this work. Having several iPhones using ONE appleID in order to sync calendar & contacts.
Can you sync two different apple IDs over the cloud? I couldn't find anything on the net.
All the best!