I'm having the same issue and it's completly embarrasing when dozens of people keep getting updates simply because I acnoledge that people decline the invitation. And it happes over and over again. Totally unprofessional!!!
When is someone at Apple going to address this issue?!?!? Hello... Anyone home at Apple? How about someone at Apple at least give a response..!!! Anyone... (All I hear is the sound of crickets chirping)
I guess I'll just go disable my Exchange account in iCal AGAIN and hope SOMEDAY someone at Apple will address this...