From the Gentoo Forums:
I agree that spreading a positive
message is good, but I've always
been nervous to send thank you
notes out to people I've never
met.
Worse, I don't want to potentially
overload an inbox with a mes-
sage that isn't going to help all
that much. Hopefully it would be
received in a positve way.
I try to remember to send "thank you"s from time to time.