I just did it. Kinda.
It has been a goal of mine for a long time, but I have never been able to screw up the courage to do it. I ended up E-mailing what was sort of a fan letter to a web comic artist I really like.
The way I did it was to ask a question on behalf of a forum I am part of. For me, knowing that there was another reason for the letter beyond just being a fan letter made it easier to write and send out.