[trashb]

> people never hold their cameras upside down

I'm not to sure about that. I rarely keep my camera (close to) fully horizontal.

[teh64]

Also for macrophotography when you want to have the camera very close to the ground on a tripod, upside down is often used.

[ryukoposting]

You don't have to. There are GPS satellites along the horizon too. As long as it isn't literally upside down.

[RobotToaster]

Turning your camera upside down is an old trick to see over crowds, since the viewfinder is now at the bottom.

[stavros]

This trick is also used extensively in submarines.