Mr Paranoid walks from one secure location to another. Mid-journey, he panicks -- his wireless device (laptop, iPad, or other common consumer electronics) is turned on! If it sent any information to an enemy-controlled access point, the enemy could identify him, or become aware of the fact that he is in this location, or perhaps deduce this from the fact that someone was in this location and everyone else is accounted-for! Oh no!
His WiFi device is some off-the-shelf 802.11 item, its software does not establish any connections automatically, but it was turned on and at the very least it was listening for access points.
The enemy has not installed any specialist detection hardware, but can run their own software (rootkits or whatever) on any other people's standard WiFi access points that happen to be in the area.
Will Mr Paranoid's device send any messages to these access points, or can it be tricked into doing so? Can the Enemy track Mr Paranoid in any way by virtue of the fact that his WiFi is turned on?