I think the idea of a "post scarcity" world is incompatible with some pretty basic human psychology. Even in the modern world, there are some resources (information) that have, for all practical purposes, become infinitely available. Yes, getting access to it isn't universal yet, but even amongst those who have a broadband connection, information is still locked away behind paywalls, media stores, etc.
This leads me to think we'll always have some kind of scarcity, even if it's artificial scarcity. Because there will always be some things that aren't infinitely available. As technology increases, those finite things won't be material, resources or even dare I say it energy but it could very well be abstract things like ideas (copyright) and inventions (patent). Part of it is probably that people need distinction in order to differentiate themselves from their peers. Another is just pure greed; some people like being perceived as better than others.