You're right, it isn't a good sampling technique. When I said "random individual" though, I wanted to state some sort of distance from the LessWrong Community. It is very possible that most people in that community know of appsumo and reddit, but since I'm outside of that community, I knew nothing about it. I suppose, in retrospect, I should have said "outsider" instead, and I also realize that the extent of an outsider's knowledge likely doesn't have any relevance here for this topic.