Security (and paper plates) aside, I just think guests should be invited, personally. And if someone gets an invitation and doesn't want to attend, for whatever reason, they can decline. Life's too short to attend events you don't want to attend, with people you don't know or like.
I apply this rule when my husband gets invitations for social events at work. I ask, "Did he invite you and me, personally, by name, in writing?" "No, just sent an email to everyone in the group." I don't consider that an invitation that's worth getting a babysitter for seven kids.
Good for you...those are great rules to follow.