Street art is often an expression of social commitment. On walls you can find critical observations of the social-economical situation of a country. I posted on this subject once by refering to Banksy, an artist who publicly criticises the policy of capitalist and right-winged countries.
Here I found a collection of anonym grafitti artists that are putting their views on society on walls: a gallery of walls with stuff written on.
[...] Bartolomeus 1 2 3 [...]