The city of São Paulo implemented a "Clean City Law" in 2006, which banned all outdoor advertisements. No billboards, no ads on buses, no posters. Within a year, 15,000 billboards were taken down and store signs had to be shrunk so as not to violate the new law
This changed helped the people of the city see things like overworked factories, and illegal workers living in bad conditions and led to a change in these problems. When the billboards were taken down, they revealed shanty towns and slums that a lot of citizens were not aware of.
This video shows some of what the city looked like before and after the law was implemented.
Now, the city has relaxed the laws a little bit--there are now bus stock and clock advertisements in the city, but it has still remained a more beautiful place. The effort put into street art and city architecture also improved, making a more beautiful city!
There are some rumors that ads will be allowed again now that the World Cup will be held there in 2016, but I can't help but hope the ban will still somewhat hold--why do we need to be bombarded with advertisements 24/7?