An excellent move by Apple in the name of privacy controls:
On the other hand, you'd perhaps want to be aware of it when designing wifi roaming controls into your APs. For example, I was thinking of using the RSSI of the Probe request as an indicator of which AP (when you have multiple APs on one SSID) should respond to a given probe. I think this feature would break that. Or maybe they do something fancy to us non-anonymous MAC addresses on the SSID you're already connected to.