Somewhat serious content alert. “Unintended consequences” is another term people often misuse. A definition posted on Wikipedia is, “outcomes that are not the ones foreseen and intended by a purposeful action.”
The “misuse” from my perspective is when a new idea is proposed and opposition to the idea is raised, reasons for the opposition may be met with a comment such as, “Oh, you’re worrying/arguing over something that won’t ever happen.” In my experience, this is especially applicable when social and actual engineering is involved. (Business, too, but I’m not going to use those examples). Those of us who were young in the 1960s, a time of much social upheaval, brushed aside a great many concerns of our parents/grandparents warning us of potential breakdown of families, etc. A number of those consequences can be seen today. Therefore, a major increase in children with no father figure and the adverse affect that can have is not an unintended consequence – it is one which was clearly stated and ignored. Yes, I realized having no father is better than a dangerously abusive one, but there are many, many studies supporting the major problem of no father figure in homes.
Moving on, however, to an example of unintended consequences (although maybe some people did warn of this) is the recent advertising for a company that provides on-line ordering and delivery of pet supplies. One of the benefits is the consumer will no linger have to wrestle with heavy bags of pet food, etc. That is true. What I recently learned and hadn’t considered is that some postal workers are having to retire earlier than planned because of the significant increase in heavy loads they have to handle. As was stated to me, via a third, “Sure, one or two deliveries a week is okay. But when it becomes almost a daily thing with multiple deliveries, that’s more than I can deal with.” When private delivery firms hire people, that is with the understanding there are likely to be heavy deliveries. That is not in general (or wasn’t) true for most postal workers. Is the adverse affect on postal workers more important than the benefit to the consumer? That, will of course, depend on your point of view.