it really bugs me when they do this. as ds1 is taken to school by a childminder, i gave the invitations to him he swears he gave them to all of the children invited and out of 20 invited only 5 replied so as we were going bowling i sent another letter to the non-repliers saying if i have not heard from you by xxxx date then i will assume you are not coming and therefore no birthday tea or gift bag will be made up for your child. still no replies from teh fifteen of them.
on the day of the party we turn up at teh bowling lane with the five who had replied and a couple of outside of school friends and low and behold 8 of those fifteen turn up as well!!!! I was furious! i made it clear to the parents that whilst i wasn't going to be cross with a 7yo i was most definatley not happy that they hadn't replied to which they just shrugged!
i really think that some people have no idea about manners, i wouldn't dream of turning up at a party that i hadn't rsvp'd too, wher one was required. Luckily the bowling lane was very good about the extra numbers as well (i think they could see how cross i was)