There definitely are ways to address the issue... figure out what can be done to minimize it and institute a cost effective solution... It just takes a desire and willingness to put forth the effort to figure it out.
There are really only three options that I see that would be possible:
1. Redesign the case, which has been stated, really doesn't help Sony or anyone else, as Sony is selling games to be played, and as long as the disc aren't damaged within the case, that's not gonna happen.
2. Include some kind of manual or padding within the case before it is sealed, which will keep the disc in place, but will also add cost, and once again, doesn't change anything except for those who are collectors and are having issues with a loose disc.
3. As LRG has stated, the last option would be to not seal the case at all, then this would allow for several different options to keep the disc from coming loose, but what difference would that make either way, as now the case is no longer sealed. And the same problemed group, is going to have the same problem.
Honestly, I've seen several issues and debates in my 35+ years of gaming, but this loose disc issue is about some of the dumbest shit I've ever seen.
As long as the disc isn't being damaged or broken by coming loose within the case, NO ONE IS GOING TO SPEND TIME TO FIX THIS ISSUE, AS IT IS NOT AN ISSUE FOR LRG OR SONY!
When you buy a game, the only responsibility is that it is new, and plays as intended. A loose disc is not a defective product, as once you open the case and play it, you can then return the disc to the holder properly, and the problem is fixed. A retail store will not take back a game in the case as loose, as it is a fine working game.
Yes, maybe it sucks that the game came loose, but shit happens, it's an imperfect world, deal with it.