It comes down to
degree of motivation. If you want folks you work with who walk past your desk or cubicle to walk away empty-handed, this will likely do that. Adding iAlertU is even better. A K lock on my PB from 2003 to 2011 did one of 2 things: 1) kept my PB safe. 2) gave me peace of mind, even if I was fooling myself. Maybe a little of both. Of course now, in their infinite wisdom, we no longer have that option available on Apple laptops. There's room for a K lock slot, they just arrogantly did not put one there. Dicks.
But
if I want your MBA, I will get it. (not a thief--devil's advocate here)
It seems like a medium cable cutter could handle the aircraft cable of a K lock, although it might take a couple minutes to really bite through all of the way (and then the thief is stuck with a laptop with a lock sticking out of it--hard to resell).
But this plastic case? (
http://www.applelocks.com/index.php/apple-macbook-locks/macbookairlock-13-combo.html) Not only is it about the fugliest thing I have ever seen, I could crunch that lock area with a garden-variety set of linemans pliers in under 5 seconds like it was never even there. Buh-bye, MBA. If my partner creates a distraction by spilling her latte on the other side of the coffeeshop, I can get away unnoticed, with your laptop. You come back to a K lock connected to a $70 broken piece of plastic.