My wife is particularly skillful at saying just the right line when she has to write a business note. People remember well-written business notes, regardless of their form. To me business notes require your picturing how the other person would react to your words. Florence Isaacs classifies follow-up notes as part of business notes. Suppose you are the person in charge of obtaining a speaker.
People like to be acknowledged for their efforts.
So few people thank that, usually, the individual is touched to receive a personal acknowledgment. To add some additional thoughts, I now like to write e-mail to colleagues I have met at a meeting or a seminar. It helps them remember my name, and I can comment on some conversation we had during the session. Often, you receive an e-mail acknowledgment that the individual liked what you said. It is good business and good networking.