I'm now wondering about the whole wifi router/MAC address connection (see p. 30). Initially, they claim they intercepted "public signals," and that from this information they were able to determine the MAC addresses connecting to the router. That's all well and good as long as you're running an open access point, but using WPA (for example) would prevent this.

Are we supposed to assume this guy wasn't encrypting his wifi? I'll grant that it's possible, but it strikes me as unlikely given his activities.

Alternatively, if the wifi router were encrypted, are they suggesting that it is "public" because it's wireless, penetrates walls, and can be "seen" from outside?

In order to inspect MAC addresses, the WPA encryption would need to be cracked using that SSID pre-computed attack. However, executing such an attack certainly couldn't be considered the collection of public information.