In reply to no_more_scotch_eggs:
It's definitely art.
Not directed at you - but one of the reasons these type of things can cause so much anger and confusion is because of a misunderstanding of the purpose of art. Many people think art is only about creating happiness and related emotions through beauty. However it's instructive to look at the development of music, which art has followed.
Music was originally only allowed (by the Church) to use perfect fifth, perfect fourth and major intervals. This basically restricted the music of the time to being happy sounding, or neutral sounding.
Then minor intervals were allowed - this allowed the representation of sadness in music.
Then chromatic notes, and more audacious key changes - this let other emotions, such as confusion, urgency, melancholy be represented.
Then keys were done away with altogether, and dissonance began to be sought - this allowed torment, anger, hatred to be represented. Perfect example - Threnody for Hiroshima.
In art, the same thing has happened. First art was about happiness. Then sadness was important. Then other emotions - and very lastly, anger and confusion. The purpose of art is to feel something - whatever it may be.
In this case, whether the artist has done a good job of that - is up for debate. I personally think it's a pretty poor way to show his claimed message (to highlight inequality). I liked this video, and thought something getting this point across would work best:
http://infosthetics.com/archives/2013/03/comparing_the_perception_of_wealth...