I still haven't started The Moon is a Harsh Mistress, but as an amusing bit of Heinlein lore, here's a post on his pre-Internet method of replying to fan-mail:
Although I'm sure those who wrote long, heartfelt letters likely found this method of response rude... I, for one, find it absolutely hilarious and would have loved to receive one!
http://kk.org/ct2/2008/09/heinleins-f...