Hello,I do not have a contribution for the "Who's using Debian" list, but I would like to inform you that Debian comes first in our "Usage of Linux for websites" survey, see http://w3techs.com/technologies/details/os-linux/all/all. You can also see examples of high profile sites using Debian at http://w3techs.com/technologies/details/os-debian/all/all.
Congratulations, and keep up the good work. - Sam