It doesn't fit neatly into the left-right divide. If you look at the political spectrum as a 2 dimensional grid with (0,0) in the center, the limits are -10 and 10, and economics on left/right and authoritarianism and libertarianism as up and down, anarchists would be (x, -10). You can basically plaster any economic system on top. IMO, they do tend to the extremes of communism and full on capitalism because it's not very practical to have a mixed market economy like ours without a government entity to do regulation.