CDs and DVDs are read by a laser beam that is trying to focus on an area that is smaller than a fraction of the width of a human hair. The problem created by sticky paper labels is that the labels are rarely ever perfectly round like the disc, and rarely are they ever applied perfectly in the centre of the disc.
The result is that as the disc spins in your drive, it will vibrate. The vibration makes an already difficult task for the drive even harder. The vibrating disc means that when the disc is read, more errors are created than are able to be interpreted by the CIRC system in your drive. If this system, that is designed to correct errors, is overloaded then you will begin to get demonstrable playback flaws.
These flaws show themselves up in music as clicks and pops, and in CD ROMS as programs than hang, are erratic, or just don't work.
So Why Do Companies Offer Discs with Sticky Labels ?
They're CHEAP!. It is much less expensive to print a label than to use professional disc printing technologies to print directly to the disc. Disc duplication companies that offer sticky labels are often unaware of the damage caused to the quality of the playback.
Don't get enticed by cheap prices. Check what is happening on top of your disc before agreeing to a quote from a duplicator.
What Should I Do?
If the playback of your content is important to you, always check to see that you are getting discs directly printed on the surface. There are 2 basic technologies that exist - InkJet and Thermal and both offer photographic results.