Hmmm... some interesting points here, but...
I still am not a fan of engraving, and I just don't see the point at all. Reminds me too much of the car alarm effect. Engraved numbers, beeping car alarms, it all just becomes part of the 'white noise' of our so-called civilization. A sad statement, upon reflection, but otherwise ignored in day to day life.
How many times has anyone called 9-1-1 when a car alarm is going off to report a theft in progress? How many times have we checked on a piece of equipment that has a number engraved on it? Beyond the cited pawn shops and repair shops, it doesn't sound like many of us follow up on this. Frankly, in reading through the posts it was only afterwards that I started thinking that perhaps I should be researching the gear that I get that has stuff engraved on it. Of course, deciphering what some of it is supposed to be might be problematic in some cases.
Seems like if there were a standard, and a central registry, then it might be worthwhile. But randomly engraved stuff that I find at Goodwill for $2 doesn't inspire me to spend too much time researching. I guess that makes me part of the problem.
And its not like engraving tools are tightly controlled, now are they? If a drivers license number can be engraved on a front panel, then it can be obliterated in like manner. And if done artfully, it might just improve the asthetics over the number my TX-2500 has on it now.
The workable ideas I heard here were the internal tag ("Help! I have been kidnapped! Call the police!") and recording the serial number and storing separately. Both sound emminently effective, and neither involves desecrating a dwindling resource.
I have used address labels, stuck inside or outside, to help lost items find their way home - like my cell phone, golf clubs, etc. I have always just gone on the assumption that if it is worth stealing, any ID information will be worth obliterating, so its not worth being destructive. A stick-on label will help the honest person reunite me with the wake of effluvia I leave in my travels...and I do leave quite a wake!
Sorry for the $5 answer to a .01 question.