I think you mean "en masse", although you might also mean dropping links to malware during a liturgical service. I don't judge.

Indeed. The people that want to spam propaganda were limited to newspapers and TV. I shudder to think what they’ll be able to do with this newfound QR power.

Pretty soon any random person will be able to put a QR code on their car.

I don't think it's any more effective than paying someone $15/hour to drive a billboard truck around town. I live in Washington DC, and I saw two of them near church this week.

depending on wether your definitions of propoganda and malware include rick astley, thats exactly what they did

the new "fly over and drop paper propaganda fliers in enemy territory" - just launch a bunch of drones to share your message and have them disperse before the authorities arrive.