I sometimes add multiple people to event before or after the event to track the activities. If I can select people from the list in bulk, it is much easier than manually putting the names of the attendees. This function can be added to the list of contacts page or to the activities page.
It is also good to have a function to add people not only to a new even but to an already existing event from the page of the contact.
(e.g. I like the way that I can choose my friends from the list when I create events on facebook)