[Frito]

The tricky part of labelling is getting them balanced. If they're off just the tiniest bit off they'll wear out the bearings in your DVD drive motor over time and kill it. I know blockbuster used to put labels on their disc and a bunch of people got new Ps2's because of it. Now they're labelless :P

Edit: In case I wasn't clear. Don't do it, just use a Sharpie.