Yes, The ps3 can smudge discs, the slightest jolt on the shelf or vibration.
No, smudges will wipe away, I broke a GT5 disc by moving the ps3 with the disc inside, scratched it good and proper.
Damn, it has the xbox 360 disease as well? Heard cases of people's xbox360 discs being scratched this way.
Nowhere near as bad, but yes.