In my opinion, musical instruments are almost sacred. Someone smashing their guitar, jumping on their piano, or kicking over their drums is committing an act of sacrilege.

An even worse form abuse is when someone takes a beautiful intstrument like the guitar and demeans it by playing completely artless and formless, a la Blink 182/Drowning Pool/Puddle of Mudd, music. If you're playing that garbage, you might as well break your guitar and put it out of its misery.