I said somewhere before that folk music is simply the stuff that folk music fans listen to. It's the stuff that folk musicians play. Folk musicians are the folks who get gigs at folk music venues. Folk music venues are the venues attended by folk music fans. We know it when we hear it. And we usually know that certain things definitely aren't it. And there's a bunch of other stuff that we aren't really sure about but we'll get back to you later after we've discussed it amongst ourselves.
Anarchism is that which is practiced by Anarchists. Anarchism is that form of social organization that exists in anarchist organizations. Anarchist organizations are those organizations that are organized by Anarchists. Hardcore Punk Shows, Independent Media Centers, Anti-Capitalist Convergence Centers, Critical Mass rides, Food Not Bombs, Anti-Racist Action, Reclaim the Streets Parties, Eco Villages, Squats, pirate radio stations, consensus based decision making, affinity groups, clusters, blocs, Chiapas, Barcelona, Paris, Djursland, the IWW. Anarchism is better defined by these experiences of radical community than by any coherrent unified principled philosophy.
I think the same frame could be applied to the question "What is punk?"
Is it any wonder that so many folk and punk musicians are Anarchists?