[jacquesm]

Why is receiving data openly transmitted on the airwaves illegal?

[lawnchair_larry]

These aren't passive devices. They have to "stomp" on AT&T's signal to get your phone to associate with them, then spoof as the carrier.

There is a loophole though - if you target a phone with the correct bands, one of the european bands is a ham radio band in the US, so licensed operators can play around that way.

Also, the DIY version is about $1000.

[emddudley]

Ask Google about their Street View wardriving project... an appeals court ruled that it violated the Wiretap Act.

http://www.wired.com/2014/04/threatlevel_0401_streetview/

[anigbrowl]

That was quite different though, because Google was (inadvertently) recording packet data as well as SSIDs. It's right there in the 3rd paragraph.