A bug has surfaced for iOS 6 users under some specific circumstances. It appears that several companies first reported in late September and it has escalated in recent weeks. It centers around meeting cancellation notices, which get broadcasted to all invitees not just the organizer.
As posted to this Apple Support forum thread, https://discussions.apple.com/thread/4351951, Microsoft and Apple appear to already working together to see if they can resolve it. Microsoft has a public article posted here: http://support.microsoft.com/kb/2768774.
Adam Glick from the Microsoft Exchange Team has also blogged about it with a few mitigation ideas: http://blogs.technet.com/b/exchange/archive/2012/10/23/ios6-devices-erroneously-take-ownership-of-meetings.aspx
On the delegation related problems, this article may assist as well: http://support.microsoft.com/kb/309185
An excellent recap, and history behind this bug that has been similar in the past is described here:
We are seeing several companies that are writing notices to their employees about this problem, and perhaps to wait to upgrade their devices to iOS 6 if at all possible. iOS 6 does have a large number of security updates, so depending on the impact the problem and how widespread it may be for your environment caution should be taken.
An upcoming iOS 6.0.1 update for keyboard, camera and Wi-FI bug fixes may also include other changes, but it is unknown at this time.