Notice that random electrical outlet that is upside down in the bedroom? Well, an electrician probably installed it upside down to indicate a switched outlet. These outlets are meant for lamps to be turned on at the wall when entering the room. Typically only half of the outlet is switched and the other half is always on, but some homes may be wired differently.
It’s safe to not plug anything in that requires the ground connection into the switched outlet. The additional weight of it upside down can cause the ground to lose contact, creating an unsafe condition considering the fixture will be turned on and off regularly. Standard lamp-cord wiring has 2 blades without a ground plug.
Another area an upside down outlet may be installed is where a doorbell transformer or security system transformer is mounted. It may be oriented so the wire runs towards the ceiling. These plugs are usually heavy and include a screw to keep the plug attached to the outlet.