I'm using that version of the Macbook Air right now. (Been vaguely wanting to upgrade for a good long while, but am too much in love with the magsafe connector and SD card port.)
The light doesn't permanently 'burn in' as you describe, but if there's sunlight shining directly on the back of the laptop I can see a (very faint and blurry) outline of the logo on the screen. Putting a sticker over the logo would fix it, I suppose, though it's rarely noticeable. (If the light's bright enough to shine through the screen, it's also bright enough that I'm squinting into the sun and wanting to sit somewhere else.)
Curious where Apple warns you not to do that. Seriously, we have users who this has happened to, and I don't believe they were in full sunlight. They work in an office.
You had me curious so I did some searching; I did find a few support threads discussing this sort of problem; consensus seems to be that it's not burn-in (which I'd find really surprising: I sit outdoors or by windows and work in bright light as often as possible (seasonal affective disorder yay) so I'd expect if actual screen burn-in was a thing, I'd have experienced it by now.) Instead it's pressure damage:
> If you carry laptop around and it's squished between books or whatever, that's how you get that. My first unibody macbook developed this issue. Now I use a hard case.
> What I suspect happened here is you had laid something heavy on top of your air so the logo disk in the lid embossed the defuser sheets.
The light doesn't permanently 'burn in' as you describe, but if there's sunlight shining directly on the back of the laptop I can see a (very faint and blurry) outline of the logo on the screen. Putting a sticker over the logo would fix it, I suppose, though it's rarely noticeable. (If the light's bright enough to shine through the screen, it's also bright enough that I'm squinting into the sun and wanting to sit somewhere else.)