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The FAA actually has a pretty decent infrastructure and plan for this, it's called ADS-B. By the end of 2019 all manned aircraft that fly in US airspace are to have these transponders.

If drones had these then anyone would be able to get the registration data directly from nearby drones, so you could see who the peeping toms flying around your neighborhood are, in real-time, on a map.

It's just a matter of time before any drone capable of interacting with the national airspace system will be required to have such a transponder. Along with that expect inspection and compliance requirements - just like for manned aircraft. You want to take to the sky outside of class G airspace - then prove your craft is compliant. Manned aircraft are inspected at least once per year, commercial craft more often, based on hourly inspection requirements. Hobbyist drone operators should probably also be trained, tested, and required to show competency at least, oh, once every two years, to prove you even know what class G airspace is, and maybe a certificate of training of some kind.

Take your drone to class G airspace and stay there and below 400 feet - do whatever you want. With a functioning transponder. Enjoy the sky, but please realize you aren't alone up there.

I think some engineering students at UC should make a few cell phone listening devices

Cell phone technology isn't very secure per se. For big brains used to work on radio devices, building a listening system wouldn't be that much difficult.
The only way to be sure that your communication remains secure, is to use end-to-end encryption.
The only way to keep some level of anonymity is to add onion routing to the equations (but due to high latency, you're then limited to texting).

and do a demonstration in front of the Police station: https://www.rtl-sdr.com/receiv...

...the main problem is that the frequencies used by smartphone aren't public (unlike your good old friend 2.4 Ghz used by WiFi, Bluetooth, wireless USB and just near everything else under the sun).
These frequencies are heavily regulated, and the mere fact that you start playing around might be asking for trouble.
(Well at least if you're only passively listening, there's less chances of being caught, and in practice you can't cause any cell network disruption).

You can see airplanes in the sky in real time, so most people don't consider transmitting their positions an additional risk. Lots of planes already have ADS-B and you can track it yourself in real time with a cheap SDR.

Missing from the summary... "HAARP is a high power ionospheric research radio transmitter in Alaska, which typically transmits in the 2.7 – 10 MHz frequency region. Under the right conditions, people can also listen to HAARP radio transmissions from virtually anywhere in the world using an inexpensive shortwave radio. Exact frequencies of the transmission will not be known until shortly before the experiment begins, so follow @UAFGI on Twitter for an announcement." http://www.rtl-sdr.com/listeni...

the internet allows even more radiostations than DAB...

...but requires a working Internet connection. Please take notice that the summary speaks about Norway. A country that is in Europe, and not even in the EU.
Europe is not a single country, but a lot of different countries, each with its local cellular service providers.
As soon as you travel abroad, you're roaming, and internet connection can get quite expensive.
Whereas DAB and FM are just available for free from the air.

Also :

- FM (RDS TMC) and DAB (TPEG) have very clear standard for emitting traffic informations, which - at least in Europe - is supported by the vast majority of hardware (in-vehicle infotainment, standalone GPS receivers, etc.)
There isn't such a clear widely supported standard on internet. Google can provide a traffic overlay on their Maps service/app, but there's no standard way for that information to be propagated to your car's computer or your tomtom.
(And again, there's going to be a lot of people use offline maps in their car or using a standalone device, because streaming data from the internet while not it your country costs a lot in Europe, and thus using Google Maps for driving direction isn't that much practical. - Not only less features, but also requires you to download maps in advance using their fugly clumsy interface. at which point a standalone device starts to sound much better).

- FM and DAB also have a standard way to do to temporarily switch channels for some critical/emergency announcement (interrupt the radio you are listening to announce that there's an accident ahead on the highway you're driving on and you need to be careful to avoid the mess on the road. Or that because of the snow, there's a barrage of snow-plows driving at 30 km/h on the same highway where you're driving 130 km/h. You can't overtake them and you need to adapt your speed to avoid colliding).
This standard is supported by nearly any in-car radio for the past 20 years (i.e.: even old FM radios that might not be able to take advantage of all the other information available on the RDS channel can at least interrupt your music for an announcement). It even works while other media sources are playing (if you're listening to music on an USB stick, modern cars will pause their own media player, have you listen to the radio announcement, then resume your music). Even works over bluetooth (with the car emitting "pause" and "play" commands over bluetooth before/after the announcement, if the bluetooth player supports it).

As far as I know, Spotifiy on its own won't interrupt you for anything but advertisement (on free accounts). I doesn't support any traffic announcement. (and it would be problematic, because it would need GPS awareness and again costly data roaming).
You still need the car being able to catch FM/DAB information to be able to interrupt the spotify playing on your tablet.

- And that's the practical implication.
Then there's the matter of taste. Some people acutally enjoy listening to radio. Because of the music program, because of the talking heads, because of the news, etc. which currently aren't provided by internet streaming alternatives like spotify.
Only provided by web radios - ie.: radio that stream also on the internet - ie.: provide over costly internet connection what they also provide for free over the air with DAB.

everybody with highschool education can build a receiver from scrap parts for it, for DAB, not so much.

RTL-SDR would like to disagree with you.

Yup, it's not the same concept of "scrapt parts" (you're referring to electronic component lying around: resistors, transistors, condos, etc.) (I'm referring on the kind of scraps I have around : RaspPis, Arduinos, etc.) but it's still quite close to what a modern geek might have lying around.
Even if QAM / QSPK are much more complicated than FM, it's still possible to hack some at home, and is much more relevant in the modern world (Except for analog broadcast radio and a few legacy handheld radio "walkie-talkie", who the hell gives a damn about Frequency modulation nowadays ?)

Sounds like this is what he did: http://www.rtl-sdr.com/rtl-sdr...

Keep in mind there is no Tetra in the US, but there is plenty of DMR & P25, which is significantly easier to listen in on.

RTLSDR has pisspoor dynamic range (8 bit ADC), sure you can do some triangulation, but it will be very inaccurate & unreliable. Also current generation technology has a bandwidth of ~10MHz, RTLSDR can only do about ~3MHz max. (example of triangulating a VHF signal here : http://www.rtl-sdr.com/triangu...) There's plenty of cheap SDR projects out there nowadays, much, much better than the RTLSDR. And if you're serious, really advanced hardware will only set you back a few thousand $$$. (http://www.ettus.com/product/details/E310-KIT)

USB DVB tuners have been around for a while now and are amazingly cheap. Like $9.99 cheap. Besides receiving compressed DVB signals, most of them also have a general-purpose tuner mode for broadcast, etc. reception, and they make dandy Software-Defined Radios (SDR) that can tune from 50-1000 MHz or more, and translate an entire 3 MHz segment of the RF spectrum for software decoding.

The cheapest ones are based on the RTL-2832U tuner chip. They are a cable-TV tuner IC coupled to a USB soundcard IC internally. Check out rtl-sdr.com for more info. The PC software to receive radio is free, mostly open source and quite sophisticated, rivaling several-thousand dollar conventional radio packages. Check out sdr-radio.com and sdrsharp.com for a couple of the many software packages out there. Cool stuff!