I've never had a disc damaged enough to even affect gameplay or playback, but some have gotten some minor scratches over time. Blu-Ray discs are supposed to be a lot less durable than your average CD/DVD, and I'm pretty sure a scratch on a higher capacity disc would be more damaging than on a lower capacity disc.

I'm not saying it's a serious issue, because all my discs are either in use or in their cases, but it can be an issue. It's not like we're robots and never drop anything.

Isn't the PS2 notorious for disc read errors because the laser comes out of alignment or isn't as strong as it was supposed to be? I can't really recall any sort of issue similar to that with a cartridge based console.