Nintendo

Nintendo Switch cartridge based games have a file that’s unique to each individual cartridge. The dumper and accompanying flash cart make use of that file. If Nintendo detects two people playing while connected to the internet with the “same” cartridge, there’s a high chance of them banning both consoles. So any used game anyone buys after this point runs the risk that someone dumped it, maybe an old owner who resold, maybe someone who bought and returned it, etc, which means even a legitimate user who hasn’t even heard of the flash cart could get banned. There’s also the potential issue of people using the tech in the flash cart once people figure out how to use those chips to sell bootlegged reproduction cartridges that have the same issue

Oh wow, so they've poisoned the used market for Switch games. That's disappointing.