Indeed - I did a bit of information collection on R1 rotted disks and found without fail they were all WAMO disks. In addition, the disks affected have an IFPI marking of 906 and/or 907 - there's one IFPI for each layer. It relates to where the glass was made.
My suspicions are that there are slight inperfections with the glass and the two layers expand due to heat at slightly different rates, causing microfractures in the glue.
Of course, this is just a DVD users best guess from all the sharing of information that is available. If we can figure this out, surely the distributors must know, and surely they'd have fixed it by now? Well apparently discs as new as Gladiator are suffering problems!
I'm beginning to suspect I just got unlucky with Aliens and that is was just a dodgy print rather than actually rotting.
I'm trying to get a DVD Rot reporting page up and running with people being able to supply the relevant information... but I think I'll just find the same info as above. Now we must ask, what are Fox, MGM etc. doing about this? If there are DVD makers OTHER than WAMO, start bloody using them!
Updatish : Just read now from a few 'experts' in alt.video.dvd that they USED to see the problem from WAMO but havn't for ages. So what exactly is going on? I'd suspect they may have fixed the problem in the US but Aus producers still have to go through the same learning process.