You guys must be upset that you didn't get any good games. Either that or there are sharkteeth in the Gamecube that scratch up the discs. I run my Gamecube games in my Wii and they've never gotten scratched or damaged or anything.
It's not the CAGs that kill discs, a lot of those turned in by soccer moms and such who don't take care of their stuff and discs. Have you seen some of the conditions those traded in Wii games are? Sometimes its hard to find a good disc out of a stack. I would say only about 50% of those disks are decent.
I also tend to recall a similar ratio of good to bad a year or so back when they went to 50% off or was it BOGO? I forget. Ended up getting a bunch of good stuff when the in store selection was still good...Warioware, Luigi's Mansion, Mario Sunshine, a couple Zeldas, etc.