I have to differ on this one. I have been using labels on CD and DVD for last 6 or so years and so far have no problem with any of those discs.
I agree, that the labels should be from reputable manufacturer and applied using an applicator.
I can see that CD could be a problem, because reflective layer is relay not covered, but on DVD where it is sandwiched between to plastic disks??
I had one CD, got from my fried, where he made his own label and used some glue to apply it. The glue eat into a CD reflective layer and lifted it off. Of course CD was unreadable.