I want to meet the article that isn’t safe to read even if you’re familiar with its content.
Non-idempotent actions often have Lovecraftian outcomes, so I can imagine...
Maybe some religious texts
A loved one's suicide note.
Well, it's conceivable that you could end up creating a separate copy of the information in your brain's neural network.
Now imagine you keep getting interrupted in the middle, but really want to read it all, thus gradually filling the whole of your brain capacity.
I’d like to think my brain does some deduplication on interrupt. Maybe when allocating large chunks?
I can’t find it anymore, but there was someone who had some home automation where they could open or close their garage door from the internet. However it would occasionally open automatically. Eventually they realized it happens whenever they opened their browser. Apparently, they visited the page often enough for it to be favorited on their homepage. Unfortunately, it was written to act on any request, including GET requests and so whenever they opened his browser to the home page, it would fetch the favicon or preview and trigger the automation.
That's not unsafe, just insecure.
The curse of being familiar with its content is that you know when the author of the article is giving bad advice, explaining wrong about how things work, or having an opposite opinion on a polarizing topic. If you are not familiar with the subject these things won't bother you.
A typical chain letter that implores you to pass it on or you'll suffer dire consequences?
The Theory and Practice of Oligarchical Collectivism (if you're an IngSoc outer party member, anyway)
One of the wonderful things about idempotency is how it enables caching in various systems.