I love this idea:
City fights illegal gig posters with CANCELLED stickers - from Boing Boing
The city council of Glasgow is fighting illegal handbills with science: they’re paying city workers to go around and stick “cancelled” stickers on all the illegal gig posters put up around town.
And they have already had an impact on some rogue promoters who have been inundated with complaints from music fans.
People who have bought tickets to some of this summers big gigs have complained, thinking that an event, rather than the advert, had been cancelled.