I think this email is remarkably effective in blending at least three tactics, only one of which is telling the recipient how he feels. The second tactic is ro

I think this email is remarkably effective in blending at least three tactics, only one of which is telling the recipient how he feels. The second tactic is rousing the other person's sense of shame: "I think this is more a matter of respect." The third tactic is making a credible and no-nonsense threat of retaliation: if you don't pay up now, I am unlikely to help you with work in the future. It's the combination of these tactics -- expressing personal disappointment, shaming the recipient, and threatening sanction -- delivered in an authentic, personal, yet still professional manner, that makes it so effective.