A shared calander has many advantages I favour above inviting people to an event especially with people I share many events with (my girlfriend for example, or my flatmates) we use this a lot. One feature I am missing tho is the option to opt out of an event of that shared calander similar to an event I was invited to. As an example my flatmates go to a concert and put it into the shared calendar. I can't go for some reason and now this event still clutters my view. Another nice feature of this would be that everyone can see who actually is participating on that event. This could be solved by using event invitation instead but as we also share our personal calanders with each other to check if someone is free at a certain time that creates many duplicate events. Also only the creator of the event then could edit things. So ether solution would be to allow invites from shared calenders and hide dublicated events from invites, or enable a participating system as used in invites for shared calenders