Exchange assigns the role of Organizer to whoever creates a meeting that has invited attendees. The Organizer receives confirmations when invited attendees accept/decline the meeting, and the Organizer is the only one who can cancel the meeting.
There’s an ActiveSync bug with using iOS devices (iPhones/iPads) to manage Exchange meeting requests, where the iOS user may become the meeting Organizer simply by accepting or declining the meeting. This issue has been dubbed “hijacking the meeting”, and when it happens the iOS user can inadvertently cancel the entire meeting simply by declining it. For accepted meetings, the iOS user may begin receiving confirmations for others invited attendees. This of course can cause mass confusion, especially when multiple iOS devices are in the mix.
This bug requires that a Windows Exchange user originally create the meeting, and that one of the invited attendees must be an external email address or list (not a user or distribution group in Active Directory). It has been confirmed with Exchange 2007 and 2010, and iOS 4.3, 5.x, and 6.0.
Apple and Microsoft are pointing fingers at each other over this issue, so it may be a while before a fix is made available. Microsoft has released a Calendar Repair Agent for Exchange 2010 that cleans up these Organizer anomalies after the fact (via a daily timer job), but it does not prevent the problem from occurring.
If your company uses Exchange for calendaring, and Windows users are sending out meeting invitations to both internal iOS users and external email addresses, the iOS users should be instructed NOT to accept or decline the meeting from their iOS device.