How is the social context different for this mural than it is for the billboard?

Compare your ideas to the ones below. What other reasons did you come up with? What is missing from this list?
The billboard...		The mural...
Billboards are made by sellers (the creators) and intended to be displayed for potential buyers (the audience passing by)..		The mural above was made by locals for the enjoyment of locals.
In other words, while billboards are made by "outsiders" who are not a member of the community who view the community as a potential market for their product.		Murals, on the other hand are often made by a group of artists from within the community or welcomed in by the community.