A recent article in the New York Times, Anyone There?, discusses the often encountered problem of sending someone an email and not receiving a response. Even when you don’t ask a direct question, you expect a response of some kind. At least an acknowledgement that the email was received. And you don’t want to ask for a receipt which is generally considered inappropriate for personal email.
So, why do so many people not respond? This article, by Henry Alford, mentions a few reasons and I add a few of my own, though, I’m sure, there are many, many other reasons.