Which can be jammed and hindered by too much external noise or similar methods that make confusing signals. Many animals that use echolocation can be disoriented and even harmed by loud abrupt sounds. It's how some Japanese fisherman catch dolphins *illegally I might add*, it's pretty brutal.

The scenario I expect to be more common is a scorched earth policy.

"Haha, you can't see me!"
*aerosol with lighter, burns entire area around him*
"EEEEE!"

Everyone proceeds to eat Fried Capello.

EDIT: That actually sounds like something you could eat, please don't eat me.