DVR on same 12v power supply as cameras?

[KEEP SAFE]

Hi, i'm running 4 analog cctv cameras and DVR on same 12v supply but have been told this is bad practice
because the DVR should be on it's own 12v supply.
Is this right? and if so why?

 

[sparkymarka]

A short or water in any of the cameras can drag all of the system down and possibly damage the hard drive inside the DVR ,
A dedicated power supply with separate fuses per camera is the best option ..

 

[footprints]

My DVR and HD video camera system uses the same power source as supplied by manufactuer (ESP) been fine for many years now.
Three of the cameras and the DVD share one box, the extra cameras have their own supply.