One of the things I'm thinking about for a sci-fi setting is to have 'replicators'. But they will be different from the Star Trek ones. If you've read or watched any "science behind Star Trek" stuff, then you know the replicators in Star Trek would take an ungodly amount of energy. My replicators would be set up by a star and protected by force fields. Plus, they can't make copies. They can only produce base elements of the Periodic Table from the energy emanating from the sun. Then they ship the raw material to space colonies for manufacture. Thus making any solar system self-sustaining. And any invasion into a solar system would be idealogical (religious or political--by anyone who thinks they know how to live your life better than you do) instead of economical.
As much of a fan I am of High Frontier space colonies, I wonder if groups of people living in enclosed environments wouldn't lead to some very eccentric societies
