1) Event types should be configurable per Org, Community, and User Group
2) Configuration of Event Types should be done via the Admin interface
3) Adding and Removing Event Types should NOT require a restart of the Liferay instance
4) There should be a user role dedicated to moderating the calendar entries
5) Events on the calendar should have a scope. Events from Groups and Communities should have the ability to be set to either appear or be supressed on parent calendars. Example Joe has a baby shower coming up. Joe's Group would have it on the calendar and maybe Joe's Community would have it. But if you are running MegaCorp, Joe's Baby Shower might not be worthy of the corporate calendar. Events going to higher level calendars should require approval much the same way as Journal entries. If you don't have rights to the parent calendar, it should pend the event awaiting approval.
Look at this Perl based Web Calendar -
http://bulldog.tzo.org/webcal/ and this one is PHP based
http://www.k5n.us/webcalendar.php. Both of these are two fairly widely adopted web based calendaring systems. You should really look at the features and functionality of these two calendars to see what a web based calendar should look like and work like.
