My favorite "dark pattern" plausibly disguised as a simple bug is that the countdown timer, across multiple platforms I've used YouTube on, doesn't work correctly and very easily will let the ad play for a second or two longer than you intend. It behaves as if it's supposed to count down to 0 one second at a time, but there's a recurring event that is run every second to see if the countdown timer needs to be lowered…
Sound like they implemented Vetinari’s clock from Discworld. That’s a waiting room clock that would slow down and speed up the seconds hand (and also the ticks and tocks) but the minute and hour hands would run on time. This was to make the waiting person extra nervous before their meeting with the patrician. He is by far my most favorite characters in the books.
Re: Dark pattern: how YouTube makes sure you don’t always “skip ad”
#301There's also this physical clock mod that runs the mechanism a bit faster before lunchtime, then slows it down again so displayed time eventually lines up with real time: https://hackaday.com/2011/01/18/the-lunchtime-clock-gives-yo...