Δαφνη Ευτυχια Αρθουρος

So I've got these blank CDs. And the packaging has instructions, and the instructions that came with one brand say not to write on them with anything but a Special Magic CD-Marking Pen Of Specialness, or else Bad Things May Occur. They specify an oil-based marker.

I've been using a Sharpie. I always have one handy.

I've had my suspicions about the nature of the SMCD-MPoS, but had not gotten my hands on one until last night. Last night there was one lying around at the dance for some reason, so I pulled the cap off and sniffed it. It smells just like a Sharpie. Of course, that's not conclusive -- it doesn't mean that the ink is exactly the same as what Sanford (maker of Sharpies) uses, but it does mean that the carrier for that ink -- the component that evaporates as the ink dries -- is the same. So far this seems much like the time I noticed that the Special Magic Etchant-Resist Pen Of Unique Acid-Proof Qualities for making printed circuit boards (actually I was making jewelry, etching designs into brass instead of circuit traces out of copper, but ferric chloride works just as well for that) smelled just like a Sharpie ... and then went on to discover that a Sharpie works better as an acid-resist than the Special For This Purpose pen did. (And came in a wider variety of sizes, to boot.) Actually, even some store-brand extra-wide-tip markers work better than the special circuit board pen did.

So the obvious question this has all been leading up to:

Is there in fact anything special about the pens marketed as CD-marking pens, or are they just knock-offs of Sharpies with the price jacked up and a bit of FUD to convince us to buy them? Or to ask this ever-so-slightly differently, is there any reason not to continue labelling CD-R discs with a Sharpie?

I haven't had any problems so far, but a few weeks may not be a valid test. Obviously, I've got my own guess already ...