Re: Probably the most asked Trek question
Greediness: Far less likely in a post scarcity society, and such an economy isn't unlikely at all given certain technological developments we may even have in a few decades (common 3D printing of almost anything, nanotech, dematerialization of products, etc) not centuries. Add to this a space faring society with nearly unlimited resources. Barring catastrophe Star Trek may actually have greatly underestimated post scarcity.
It is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring. Carl Sagan