[o0-0o]

I tried to get this to work on my MBPr, and sadly it did not work. It might have been my lack of prowess, but it's pretty straightforward.

[zhovner]

First you need to disassociate wireless card using Apple80211.framework:

  /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -z

Then you can change MAC-address:

  ifconfig en0 ether aa:aa:aa:aa:aa:aa