tcj -
I agree that the alcohol will dissipate very quickly (having a low vapor pressure does this). However, I think it is probably on there long enough to dissolve a little of the face, and depending on the CD quality, it may be enough to destroy the integrity of the CD.
To back up my assertion, I did try looking at the Sanford site (Sanford makes Sharpie markers) and could not readily find any info there. However, doing a further search on this topic really brings to light that this is a highly discussed topic. This media supply company has a specific recommendation to not use Sharpie (or other solvent based markers) on CD/DVD's.
http://services.mediasupply.com/cd_d...on/faq.html#q6
I think this is something for the Mythbusters!
-ridgeln