ahhh... Gone are the days of writing on the toilet walls.... that's what we used as a discussion board, back in the days.
All you needed was a permanent marker, only time the boards used to go down was when there was a problem with the pluming, and the had to be closed for a bit, but the up-and-running rate was 99.9%.
Sometimes we'd lose the boards, it would just completely disappear, when they repainted the walls.
Only backups would be taking a pictures.