In the LAT Calendar, Meghan Daum takes a critical look at air-hugging, which, she argues, exists uncomfortably with that other social phenomenon, air kissing:

The air hugging phenomenon would be perilous enough if it had outright replaced air kissing. But more often than not the air hug is combined with the air kiss, resulting in a botched job on both scores. We'll see our friend or acquaintance, move in for the air kiss, and abort at the last second in favor of an upper body embrace that involves as little physical contact as possible. Just as a well-executed air kiss suggests lip-to-cheek contact without actually making it, the air hug is kind of a limp version of that "hug a tree" posture best known to yoga classes and gyrokinesis exercises.

Daum (who, full disclosure, is a fishbowlLA acquaintance-- in fact, I'm pretty sure we air-hugged once, but frankly I was pretty drunk that night and it's all kind of blurry) advocates an air-hug roll-back along with an air-kiss educational program in elementary schools to ensure proper etiquette and safety. As for me, I'm honing my air-footsie technique.