You can damage a water heater - especially a gas or propane fired unit - due to mishandling during transport and installation, and we see the resulting problems are home inspections.
For example in the case of gas water heaters, inside the heater's flue there is a piece of metal called a "turbulator plate" that hangs from the top of the flue by two small metal "ears".
When the heater is laid on its side for transport the ears sometimes slip past the top of the flue and the when the heater is set upright the turbulator falls down the flue and rest on the burner. If the installer does not notice this has happened, the heat from the burner softens the metal turbulator and it can fold and collapse onto the burner:
At a minimum this will decrease the efficiency of the water heater, it may also shorten its life and/or create a fire hazard.