They are a frequent tool of advertisers (particularly of events, musicians and films), propagandists, protestors and other groups trying to communicate a message.
Then there were the animal rights protestors who demanded that horses never do what comes naturally to them, pull a car and jog along the equivalent of a country lane.
The unjustified arrests of journalists, representatives of youth organisations and civil activists, the banning of peaceful protests and the use of physical force against protestors are therefore unacceptable.