In the news today, there's FTX (we won't even talk about something like Mt. Gox). https://www.coindesk.com/policy/2022/11/11/ftx-files-for-ban...
Recently, Insteon's entire IoT software platform suddenly and unexpectedly shut down when the company failed. https://www.iotm2mcouncil.org/iot-library/news/iot-newsdesk/...
You may remember streaming video service Quibi suddenly capsizing and disappearing a couple of years ago. https://www.theverge.com/2020/10/22/21528404/quibi-shut-down...
It may be pushing the definition of a hosted software system, but who could forget MoviePass? https://en.wikipedia.org/wiki/MoviePass
A particularly weird one was Murfie, where you sent them your physical CDs to rip and stream, and who then suddenly disappeared leaving many folks' music collections in the lurch in a warehouse somewhere. https://www.theverge.com/2019/12/13/21019565/murfie-madison-...
Oh, let me add one more. Gobbler was a popular backup storage service for multimedia creators who one day just... lost everything when they didn't pay their cloud storage provider. https://gearspace.com/board/music-computers/1100884-psa-gobb...
These are just recent, high-visibility ones. Any number of smaller players have suddenly been yeeted into the sun.