[trimtab]

If every DC Starbucks is serving WiFi via a single network vendor like AT&T etc. then the surveillance is already in place. Particularly, if only metadata is being collected.

A specialized device is not really needed. Just a Mitm position between the stores and the Internet.

[efes]

You need access to LANs themselves to get ethernet addresses which would easily map to people on many devices. De-anonymizing based on traffic in a cafe is going to be a bit more complicated than average for some users and the random passerby who accidentally connects.

Besides, how can I be sure the people I am tracking actually work for the NSA? I refuse to do blanket tracking just to catch a few criminals, that is unethical.

[tlrobinson]

I believe the article was suggesting foreign intelligence agents could set up an ad-hoc surveillance network this way. It would be much more difficult for them to gain a position directly between the stores and the Internet.