Originally Posted by DrageMester

CD and DVD media are different as to how much protection they have from the label side. For DVD media the data and reflective layers are in the middle of the disc with 0.6mm of polycarbonate on both sides. For CD media there is only a very thin layer of lacquer on top of the reflective side, an for some (older) CD-R media the top layer *is* the reflective layer.

Thus it's possible to say that for DVDs it's going to be very difficult to damage the data or reflective layer by writing something on the top or label side.

For CD media it's not so clear. Most people get no problems from writing something with a suitable (soft tip) pen like a Sharpie on CDs, but a few people have reported problems.

As long as the shiny silver top is protected by a layer of lacquer, I don't see why there should be any difference between labelling those and labelling branded CDs.

There is a sticky thread on this subject: Okay to write on discs with a marker?
I intend to move the posts in this thread into that other thread, so please look there when this thread disappears from view.