Foam Rubber CD Box Inserts: The Silent Killers?

No, it's not a Halloween topic. Bear with me, folks.

Today I picked some double CD box from my collection (Brahms' Deutches Requiem with Previn) and to my horror, the sponge-like square insert-thingy that divides the two cd's in the box had desintegrated completely and now resembled a sticky orange fungus that completely covered the label-side of the cd's.

I hadn't played this particular CD in years (in fact, it was one of the first I ever bought) and apparently, the foam rubber material had undergone some disasterous chemical transformation over time. Luckily I managed to get most of the sticky stuff off the cd's with the help of a soft brush and lots of white-spirit. The cd's appear to be still playable, luckily.

So after this ordeal I went through my collection, opened all double- and triple/quadruple CD-boxes and removed all the similar foam rubber inserts. They're useless anyway.
Didn't encounter more "bad cases", but some inserts had discolored already and felt sticky on the surface. Would be a matter of time before they'd have turned into cd-fungus too.

Did anyone else encounter cd-horrors like this?
Also, how about cd's that suddenly become unplayable? Happened to me with one of my first CD's, an expensive purchase it was, too. Grieg's Peer Gynt Suites with Karajan on DG. The cd looks perfectly normal, no discoloration, but when I feed it to any cd-player, I only hear horrible distorted noise. The dreaded cd-rot? I tried some more cd's from the same era, DG and other brands, but they played fine. Weird.