Laptops don't need screens protectors for the same reason flip top cellphones dont: Because the design protects it! Devices mainly get scratched when on the go, not when your using it.
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The MacBook Air (and all other laptops) are designed so the keyboard will never touch the screen. Its physically impossible providing the rubber strip along the edge of the screen is intact. And even if the screen could touch the keyboard, the damage would be minimal.
Mr Sir is correct. It's (or should be...see comments below, a non-issue).
If you are
that concerned, just hang on to the paper/cloth that Apple delivers your laptop with...works great...
until you realize, again, it's a
non-issue
One thing that's always nice to carry with you in your computer case, pocket or purse is a micro fibre cloth...you can get 'em anywhere, non abrasive and do an excellent chance...even dry, to dust or clean the screen. I recommend either iKlear (I believe, sp?) or the "Monster" LCD cleaning kit...BOTH of which come with a cleaning solution and a collection of different M/F cloths to use. As well, if you own an iMac, they have excellent cloths that you can also use for your MB/MBP/MBA. They may also fit between when closed, albeit you won't close it all the way...and could cause
more damage than it prevents...again, see below
The thing is I get contact points from the keys that are visible on the screen when I open it up. I wasn't worried about scratches or anything, just about the marks the keyboard was making on the screen when the lid was closed.
I'll look at the cloths linked here and probably choose one of those, thanks.
What in the world are you transporting your laptop in? Are you 'crushing' or 'smashing' it together with other items? Books, chargers, etc? Always good to use a sleeve, or laptop case for transport that includes 'cushioned' protection between the computer and other storage necessities. IE; chargers, pens and pencils, books and notes and yada, yada...you get the idea. In typical, everyday transport...there should be NO reason to get key marks on your screen...it's been several years since I've seen that issue and none of them on the couple dozen "Apple" laptops we've owned over the past decade (we run an all Mac business), I've YET to see any kind of keyboard imprint (other than the usual dust that builds up) that can't easily be wiped (typically dry) from the screen.
Sorry...don't mean to come of flippant or to talk down to you. We all have BUSY lives..especially those of us that rely on the laptop as a real workhorse and they TRULY are mobile devices. I empathize...I carry BOTH a 17" MBP and an 11" Air with an iPad2 everywhere I go...we run an A/V production company...and it's necessary to have all three tools on site, all the time. I've found very efficient ways to carry the gear...and avoid damage

If you need more insight, please send me a P/M
I hear this a lot, but every Apple laptop I've ever had, from the 5300cs to the Powerbook G3, Powerbook G4, and now the MacBook Pro print the outline of the keyboard on the screen when they're packed in a backpack.
They may be designed not to touch the screen when closed, but any pressure against the clamshell will cause the keyboard to touch the screen.
Again...not sure how you're transporting, see above. And I'll admit, I didn't transition back to Apple until the release of Intel Procs...so the earlier 'ClamShell' design may have been different...although, I don't see many complaints on Google Search for this issue...if anything, Apple (and other laptop/Read: PC Manufacturers) have been WELL aware of this for quite some time. The display is a relatively expensive fix...and if indeed there were scratching issues on a specific model, it would seem the outcry would be significant.
My conclusion (we have 9 laptops in the field right now--4 Airs, 3 MBPs, and 2 older PowerBook G4 15"ers for P2 offload in the PCMICA slot--a proprietary Panasonic video storage card--and Sony's SxS--)...don't worry about a screen protector. Your computer is built to use. Use it.
J