The poop on the issue. When it comes to space the prevailing view is, space is for professionals and please don't try this at home. If we as a developing space ferrying society, we need to think of what "human" cities would be like. Whether the cities have a population of 1000 or one million, it all boils down to infrastructure and technology. How does water flow in microgravity, or do we use water in getting our <<stuff>> together. There are many techies that are developing better water purification systems here on Earth. The only problem is that they seem to go no where outside the lab, and nothing changes in the wake of these new techniques. What happens when you are transporting 900 + passengers to Luna or Mars? How much water, food and means of dealing with all the human waste? Astronauts will forever play a vital role in space exploration, but the rest of us peons should never be taken for granted.