I think that by now apple should have solved this. If you happen to change the password for iCloud the updates of iCal, Address Book, etc. will stop on every device until the new password is entered. This everyone agrees is "acceptable". What is not acceptable is that individual devices with the old password will not alert you that the account in no longer accessible (only mail does an alert). I think that apple should realize that part of iCloud is ensuring all devices can access the accounts they are tied to, so a once a day check with warning would be welcome.