I have to admit that I am a culprit of this - how many people go to a show and spend all day wondering who people are and not introducing themselves? Then end up going home not really knowing anybody else!
Sometimes it is all too easy just to stick with the people you know.
So if you see a crazed woman with a baby on her arms going around saying "who are you?" etc. thats me!!
Either that or I will organise a little circle time where you have to introduce the person sitting on your left! (There are a lot of icebreaking games I could dig up! I am a teacher after all!!)