I received Memoir '44 in a trade but discovered that exactly one "Assault Center" card was missing. I emailed the Days of Wonder customer service to see if there was any way I could get that one card and they responded right away by mailing me a replacement card at their expense! Happy to keep buying Days of Wonder products!
My example isn't from Memoir 44 but from Shadows Over Camelot. My copy had 5 Picts and 3 Saxons instead of the usual 4 of each. I sent off an email to their customer support and they sent me a replacement in a hand written letter!
It's a minor thing but it was really nice and I have highly recommended their games and the customer service to my friends.