[jojobas]

Let's say you followed all of the leads down to connection points.

Randomized MAC connecting to a MacDonalds free WiFi, cameras capture a masked guy in a hoodie or black Cutlass with unreadable plates. Now what?

[sterlind]

even better: throw away a raspberry pi that automatically connects to the McDonald's WiFi at night from the trash can. the evidence is disposed of, and surveillance captures many people throwing away trash. whose happy meal had the toy?

[jojobas]

Or fashion an cantenna and connect all the way from KFC.

Plenty of ways to be untraceable unless there is a spook at every hotspot, instantly notified of undesirable activity.