I think the idea that one human not believing in the existence of another is in some way rude or disrespectful has already been somewhat established
Homer: You monster! You don't exist!
Ray Magini: Hey! Nobody calls me a monster and questions my existence!
Some research says that lurkers make up over 90% of online groups. I suspect that Less Wrong has an even higher percentage of lurkers than other online communities.
Please post a comment in this thread saying "Hi." You can say more if you want, but just posting "Hi" is good for a guaranteed free point of karma.
Also see the introduction thread.