Interplanetary travel is possible, but likely to be quite expensive. However Stross speculates that the more important point behind planetary travel will not be the "how", but the "why" of it. Stross quotes Bruce Sterling:
I'll believe in people settling Mars at about the same time I see people settling the Gobi Desert. The Gobi Desert is about a thousand times as hospitable as Mars and five hundred times cheaper and easier to reach. Nobody ever writes "Gobi Desert Opera" because, well, it's just kind of plonkingly obvious that there's no good reason to go there and live. It's ugly, it's inhospitable and there's no way to make it pay. Mars is just the same, really. We just romanticize it because it's so hard to reach.He largely poo-poos arguments like manifest destiny and making man immortal among the stars. Honestly, I don't think these are concepts we can just hand-wave away. Stross dismisses them because he can't see people investing in endeavors they can never personally benefit from. I disagree. For centuries people have done things, like the global explorers of centuries past or the environmentalists of today, which benefit them little but benefit coming generations greatly. I've heard that the Japanese have 100 year mortgages in some areas. Mortgages that they take knowing they will never be able to repay. I don't think Stross understands human nature as well as he thinks he does.
I can foresee a future where the Earth may be vulnerable to a mass cataclysm. For the first time ever, we have cheap and easy global travel and communications. This means that diseases can spread incredibly fast, potentially faster than we can react. It also means that ideas can spread incredibly fast and, as the world grows smaller, ideological diversity may shrink as well. This means that the entire world may be open to a social cataclysm similar to the coming demographic collapse of Europe. Given that kind of situation, interplanetary colonization might be a good idea.