[teiferer]

Though demonstration organizers could run around with QR codes making it easy for everybody to install the right app to communicate with each other during the demonstration. As long as people can side-load things on their phones, this should be possible without any way to stop it unless you deploy radio jammers. (Which is then the logical next step for police equipment in so minded states.)

[al_borland]

People are supposed to scan a sketchy QR code to side load an app? That sounds like a security nightmare.

Those working against the demonstrators could send people out with QR code to infect the phones will malware for their own means.