I think you're missing the point. Sending a thank-you note to a 200-person list is a waste of time and rude to those who don't send such notes at every occasion

I think you're missing the point. Sending a thank-you note to a 200-person list is a waste of time and rude to those who don't send such notes at every occasion. If you need acknowledgement than what's better than knowing that other person has read your email? (the default behavior of Facebook messages by the way). It is however another matter if the person who read your email decide to not reply back. I think this article makes a lot of sense.