As the thread starter and the one who asked for opinions, let me butt in before this thread descends into virtual chaos.
gmikesell's picture of an Air with an engraving on the lid was definite proof that engraving is possible, and more so for me because I don't want anything as fancy as he/she got.
Oracle1729 further added to gmikessell practically verifying the possibility.
Even though Oli3000 might have claimed to not checking the facts before posting, he/she did point out that I have to watch out for exactly what lasers are being used to do the engraving.
In conclusion, it means I shouldn't just walk into any engraving shop and toss them my future Air.
So my thanks go out to gmikesell, Oracle1729 AND Oli3000.
Having said that, Oracle1729 and Oli3000, please make up. We already have enough members ripping one another apart over claimed lack of knowledge, but we're all human and we make mistakes.