Imagine, please, that city_name.crime911.org is a web server with the ability to:
- receive #911 calls from smartphones;
- convert the current GPS coordinates for a phone calling in to a street address;
- locate other smart phones within reach of the same, and adjacent, forwarders (e.g. cell towers);
- text the originating phone's owner's name, photo, and location to those other phones; and,
- both record and forward whatever audio or video that source phone is transmitting to all of those accepting the call.
In use that technology could lead to the resurrection of the civil posse, a series of new hit series on TV ("Europe's funniest crimes", "American criminal!", "When good posses go bad") and the erosion of the crime prevention justification generally offered for CCTV use by municipal and other police forces.
In reality, CCTV use doesn't reduce violent crime - but this would, and without eroding individual privacy the way CCTV does; because even in places like Canada and San Francisco where only criminals are allowed to own or use weapons, the crime911.org service threatens the criminal with what he fears most: prompt and effective public response - even if all that means is that people flag down passing police patrols to point them at the crime in progress.
So how hard is to set something like this up? Technically, not very: in practice it's a matter of will, law, and money - all of which the big telcos selling smartphones either have or can manipulate.
So will this domino fall? My answer is that it will: just as soon as some country, probably in eastern Europe, removes the civil liability risks attendant on doing it and local results force the rest of the world, piecemeal and screaming in protest all the way, to follow suit.