Two things stick out in my mind. The first one is when my Aunt's Android tablet got all of its photos infected with David Hasselhoff. She didn't realize that the pictures were duplicated (so the originals were still there), so she was extremely upset that all the pictures of her late husband were photobombed with "The Hoff" (she's in her 80's, and doesn't even know what a photobomb is).
The second incident is the Google "Drop Mic" email reply button, that got accidently clicked on and caused some number of people to lose prospective business opportunities.
Now, the april fools jokes that aren't harmful are things like google maps having a pacman mode available, or when Slashdot did their "OMG Ponies" theme.
Thank you for mentioning David Hasselhoff. Until you did I didn't realize it was an April fools prank but instead thought it was a clever Google Easter Egg. My only photo with The Hoff is also one with the Queen Helen Mint Julep Mask which became a reddit mini-meme on its own. I figured some Google programmer was actually looking for people in green faces and didn't make the connection to 4/1. Thanks for clearing it up.
LineageOS added an irremovable notification saying "your software is not genuine" to Android for April fools. However, they have weekly updates, and I got this notification before April 1st. The only way to remove it was, as root, flip a setting. Needless to say, I and a lot of other users, were pissed.
When the April Fools prank is harmless, obvious, and doesn't affect users, it isn't a big deal. In the above example, has the notification had a dismiss button saying "April Fools", I would have not cared, and probably have been amused. But when your April Fool's "prank" affects other people, then it isn't so funny.
It's not just April Fool's, either. Antd got into a bit of hot water late last year because it was discovered that they included a Christmas theme that got automatically enabled on Christmas and didn't tell anyone about it.
At scale, anticipating the interactions your code is going to have with the rest of the world is very difficult. See, for instance, https://www.computerworld.com/article/2517969/google-s-pac-m... . It's hard enough for normal code, but April Fools tends to exercise some very undertested pathways in both code and organizations, and the results are often unamusing, and potentially serious.
Google and Microsoft and such are the behemoths of the computing industry, and the metaphor works fairly well this time; imagine a giant trying to figure out how to "prank" all the Lilliputians around them. It's gonna end up with squashed Lilliputians, no matter how careful you are.
Leave it to smaller entities.
(Although I do want to say I'm speaking about "pranks" here, like hacking Gmail, or changing the Google homepage too much. Putting up a fresh new website with something fun and cool, something that you have to choose to go to, is fine. But that's not really an "April Fool's prank" anymore, just some new fun and cool site.)
It's because the crowd here is very old. I think the average age is in the 40s or 50s. It's essentially CNN's demographic and a significant number of journalists and media people here. There really is nothing "Hacker" about hackernews. It's pretty much "news". How often do you see the irreverance, humor or anti-authoritarianism of hackers here?
The second incident is the Google "Drop Mic" email reply button, that got accidently clicked on and caused some number of people to lose prospective business opportunities.
Now, the april fools jokes that aren't harmful are things like google maps having a pacman mode available, or when Slashdot did their "OMG Ponies" theme.