I turned on (for a few minutes) deletions of iCal events. Some of my calendars are hosted in Exchange and some on Google. Some of these events are group meetings with group scheduling in place. My calendar appointments with other individuals are both inside the “Exchange” and/or “Google” space and outside.
iCal is notifying all these individuals of the deleted group meetings (from 2 or more years ago since I said delete after 730 days) that the meeting has been canceled. Of course, it happened long ago — it was not cancelled. Alas, all of these individuals are getting e-mail announcing these cancelations from me (via automated iCal behavior).
Broke, broke, broke!
(bug report submitted to Apple, there are discussions in the Apple Forum on this issue.)