For every fiery screed or gushy, tear-streaked confession in the ethersphere, it seems there’s a big patch of grainy, unresolved black. Though it would comfort us to think that these long silences are the product of technical failure or mishap, the more likely culprits are lack of courtesy and passive aggression.

“The Internet is something very informal that happened to a society that was already very informal,” said P. M. Forni, an etiquette expert and the author of “Choosing Civility.” “We can get away with murder, so to speak. The endless amount of people we can contact means we are not as cautious or kind as we might be. Consciously or unconsciously we think of our interlocutors as disposable or replaceable.”

Judith Kallos, who runs a site on Internet etiquette called netmanners.com, said the No. 1 complaint is that “people feel they’re being ignored.”

I certainly felt ignored when a young editorial assistant at a magazine asked me to send important information to her but never acknowledged receipt of same. I waited 72 hours for her reply, and then sent the information again with a note saying, “Just re-sending in case you didn’t receive.” When another 48 hours elapsed without a reply from her, I resent the information again, this time appended, “I’m resending this because I have no way of knowing whether or not you received it.”

Some six hours later, I started composing a third note — “Could you tell me if you’ve received this e-mail, please, as I am about to have a small sliver of my brain removed in surgery, and would love for this sliver to be unclouded by doubt”— which, fortunately, her response minutes later kept me from sending.