1. Sets out the problem with traditional justifications for state power
2. Outlines a path to minarchism
and, most importantly,
3. Helps us to avoid coercion in our personal lives.
For a good example of 3, check out Jack Crow's sidebar about how he hates the English language's use of possessive words to indicate association (my wife, my kids, etc).For an exceptional example of 1, check out Prof. Coldheart's comment from ages ago:
My ultimate point: we are already living in anarchy. We are already living in the world that you predict anarchy would turn into - a world where the biggest gang has grabbed all the guns and cowed everyone they can't shoot. That's the state of affairs right now. Anarchism, as a philosophy, simply exposes that. Anarchism states that the idea of Power Subservient to Justice - a/k/a, a benevolent State - is a myth.
On this view, anarchism is of similar practical use to atheism: neither provide much in the way of positive instruction, but both are very good at puncturing delusions. Another parallel: think of a-theists as similar to anarchists like the good IOZ, living in a State-dominated world but believing none of it, and anti-theists as more revolution-oriented anarchists.
We ought to call those folk the New Anarchists, probably - although the first anarchist theorists were revolutionaries, well before them came the peasant, groaning under his burden, who decided that maybe the king wasn't quite the divine leader he was cracked up to be.