Is this really needed?

Sticker on the ceiling, Ramada Hotel, Vancouver, BC 

Common sense is far from common. And perhaps that is why notices like this are needed.

When a fire sprinkler is triggrered the mess is remarkable. Thousands of litres of dirty water can do a huge amount of damage. My guess is that this notice is on the ceiling because someone hung something from the sprinkler head, triggered the sprinkler, and made a hell of a mess.