A guy did a torture test to determine if the Blu-ray disc really stood up to abuse. It did. From the bottom paragraph of this article:
"...He rubbed the data side with steel wool; it still loaded. He tried scratching it with a ballpoint pen; it still loaded. He took a pizza cutter to it; is still loaded. It wasn’t until he gouged the surface repeatedly with the point of a Norman Bates kitchen knife that the poor BD refused to load. ..."
He also published this video.
"...He rubbed the data side with steel wool; it still loaded. He tried scratching it with a ballpoint pen; it still loaded. He took a pizza cutter to it; is still loaded. It wasn’t until he gouged the surface repeatedly with the point of a Norman Bates kitchen knife that the poor BD refused to load. ..."
He also published this video.