[Guy Harris <guy@xxxxxxxxxxxx>]

BTW, none of this is specific to the MacBook Air, USB Ethernet interfaces on OS X, or, in fact, to anything other than OS X.

The notion of changing the ownership of the BPF devices to allow non-root capturing isn't even specific to OS X - it also applies to {Free,Net,Open,DragonFly}BSD, and to AIX, although the way you arrange that the device ownership persist across reboots would differ from OS to OS.