Just to make this accurate. The digital information is just underneath the printed side....the rest of the underside of the disc is just protection. Hence the need for CD pens for homemade CDRs. (Early commercial CD's were printed with "Acid" inks, that burnt through the top side, destroying the data lurking underneath!).
And I've got several CDs that prove it!
So, I actually look after the label side of a commercial CD as well as the shiny side!!

Basically, they are delicate beasts. And affixing labels of any sort is not a good idea! If you have any of these, Transfer them to a hard drive as soon as possible.....The glue on the label will bleed eventually, maybe destroying the CD and damaging the M/C or computer that you are using.

And remember....NO BIROS!!!!

It's just the way that are made. It's just amazing that the buggers work at all!! Get a big hard drive, and copy all your favourites to that. Then you can use the CDs in the car or wherever, safe in the knowledge that you've got a back-up at home....

I've got very anal about this, and I've actually got 2 hard drive back-ups for my most treasured recordings. The second one is kept in the dark in a constant temperature room....I rarely look at it, but I know it's there if I need it!