IMessages sent to additional people in address list and other major errors.

Question

Just noticed a MAJOR security and privacy problem with iMessage last night. Wonder if anyone else has seen the same. Here's the scenario:
I (3GS, iOS5) receive an iMessage from person A (4, iOS5). At the same time, the iMessage from person A ALSO goes to my wife (4, iOS5). She responds via iMessage since she doesn't recognize the number. The response goes to person A and also appears in my iMessage conversation thread with person A as if I sent it (i.e., appears in blue on the right side of the screen).
My wife also gets my responses to person A and they all appear in a thread between her and person A (i.e., person A's number at the top of the screen) as if they are coming from her phone (i.e., appears in blue on the right side of the screen).
Both my wife and I "receive" iMessages from each other that appear as if they are sent by ourself and not the other person (i.e., appears in blue on the right side of the screen).
Summary: an iMessage meant for me sent from another person, also appears on my wife's phone. She can see the conversation between us under a thread under this person's phone number. If I send an iMessage right to my wife, she only sees it (not person A).
Some more detail. My wife and I have totally seperate billing accounts. We both share the apple id for appstore purchases. She has her own iCloud account that's different from mine. Also, the first messages between person A and me were text messages (as I was out of the country, no Wifi). The mixup only started to happen when it switched to an iMessage when I got back in the country. Person A only has my phone number and not my wife's at all in his contacts, so there's no way he could have intentionally or accidentally sent the message to both of us.
This is a MAJOR security and privacy issue. Has anyone else noticed this weird behavior or have any idea how to fix it.
Thanks,
JMR

Answer 1

Under settings -> Messages -> Receive At check what you and your wife have set up there.  You may have duplicate identical phone numbers or email addresses there, which may explain why you both get the same messages.
Your primary iMessage account IS your Apple ID, so if you both have the same Apple ID (and thus also the primary email address linked to your Apple ID), then you are in fact sending from the same iMessage account.  In that case, your only way to avoid the mess you are seeing is to set up another Apple ID for one of you to use.  An iCloud alias is not goint to change your iMessage account It will allow you to set up distinct "receive at" email addresses, but your accounts will still be the same.
P.S. the "Caller ID" section there will determine where your messages appear to originate from.