I'd like to say that I was drunk and had a brilliant idea - or that I was making a sandwich whilst hovering over a pile of CDs - but the truth is that I went searching on the internet. I think I googled "sticker residue remove how" and one of the pages mentioned it. The thing is, there were about 25 different suggestions, but they all involved products that I either didn't have in my apartment or that wouldn't be easily obtainable here in the Land of the Morning Calm (which is a misnomer if I've ever heard one). Most of them mentioned techniques and gave instructions, but one just said "Mayonnaise" and I thought, well, I have that in the fridge and it certainly can't *hurt* the CD cases, so what the hell... WD-40 was one of the other suggestions.