I know they say 20% of your invites will be declined, but I've been really disappointed by friends saying they aren't coming. So far only at save the date stage and 3 friends have said they aren't coming.
One is a very good friend who has known the date for a while and was excited about it, but has now said she can't come as she's going on holiday.
I do have a newborn so perhaps my hormones are crazy, but I had a cry after she told me!