Could work both ways. If someone receives an iPod with personalized engraving they would possibly be more likely to hold onto the device longer since the object now has some sentimental value. For re-sale the engraved models sell at a lower price which makes the second hard market more attractive to thrifty buyers. I suspect xenophanes is right -- Apple wants people to buy iPods directly from them instead of other resellers who might put competing products side-by-side.