I communcate with lots of academics regularly, as I'm sure most readers of this blog do. This is not surprising. But what I do find surprising is how frequently academics simply do not respond to, or even acknowledge, communications from professional colleagues. This includes communications of the following sorts: invitations to give a talk, invitations to contribute a paper, invitations to review a paper, messages sharing a copy of published work that engages their views, messages sharing in-progress work that engages their views, and messages asking specific questions about their own published work. (The list is not exhaustive.)
Of course, many of our colleagues respond promptly and helpfully to such messages. But it's still amazing how many simply ignore communications –– including short, polite follow-ups to the initial short, polite message. Not even so much as "Thanks, but I don't have time" or "Sorry, I'm no longer working on that topic." In many cases, it's clear that simply ignoring the message interferes with the sender's ability to effectively discharge professional responsibilities (e.g. organizing a colloquium series or an editor's responsibility to secure timely review of papers).
Life's too short to get bitter or dwell much on such slights, but I did want to hopefully start a conversation that raises awareness and to see if others had thoughts about this unflattering aspect of our profession, including what sort of attitude is warranted toward offenders.