Bruce Sterling, Holy Fire(1996). Notable for its two tier currency and stipulated "basic necessities" sphere of exchange. I think this is a trope that crops up in a few different incarnations: compare e.g. Karen Lord's Galaxy Game ('"Economic credit is mere financial engineering," sneered his Academe guide. "Social credit is art"'), or the basic necessity makers in Cory Doctorow's Down and Out in the Magic Kingdom or Neal Stephenson's The Diamond Age.