Mine isn't checked to begin with, yet I'm still receiving emails when my wife updates events in a calendar she's sharing with me. Same thing is happening with one of my co-workers. Seems to coincide with when I updated my iPhone to 5.1.Login to your icloud.com account (web), click the shared calendar symbol on the right of the calendar and uncheck the "email" box.
I have two shared calendars; mine and my wife. We both have edit permissions on both calendars. On my calendar under sharing (icloud.com) I have the notify me by email when changes occur. For her calendar under my icloud.com account I don't have that checked. Its just the opposite on her icloud.com sharing settings.I noticed this too - but then I thought that maybe if I check the box that means the people I'm sharing with will get an email that I, myself, changed the calendar (for example). Like, by checking the box I'm effectively adding a Push notification FROM me to them.
Or is it the other way around... (head spinning)