It turns out that in the current version of the macOS, the OS sends to Apple a hash (unique identifier) of each and every program you run, when you run it. Lots of people didn’t realize this, because it’s silent and invisible and it fails instantly and gracefully when you’re offline, but today the server got really slow and it didn’t hit the fail-fast code path, and everyone’s apps failed to open if they were connected to the internet.
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The good news is that Apple has, just today, publicly committed, presumably in response to this page, to:
deleting the IP logs
encrypting the communication between macOS and Apple to prevent the privacy leak
giving users an option of disabling these online checks that leak what apps you’re opening and when.