Scoble asks "How do you persuade?" in which he poo-poos consistent positive statements and talks up authority. It turns out there are scientific studies. According to Robert B. Cialdini's February 2001 Scientific American article "The Science of Persuasion" (my research library can beat up your research library!) the 6 keys to reciprocity are: reciprocation, consistency (get people to say "yes"), social validation (many people doing it), liking, authority, and scarcity. Cialdini has a book: "Influence: The Psychology of Persuasion." I guess I found Scoble his Christmas present.