O'Neal colonies are utopian and impractical. Ten thousands years from now (hopefully) most of the human race will be living in spun-up hollowed out nickel-iron asteroids. However the industrial infrastructure to hollow out an asteroid and then ship volatiles to it will be enormous. Establishing a canyon colony on Mars is almost trivial by comparison. Mars has a much more shallower gravity well than the Earth. Therefore Mars is a more practical jumping off point for establishment of asteroid colonies (Mars is closer to the asteroid belt as well).

As I see it, human space colonization follows this path:

1) Skip the Moon and libration points.
2) Colonize Mars and become self sufficient there.
3) De-industrialize and depopulate the Earth turning it into a big wildlife park / museum.
3) As the resources on Mars depletes, mankind's population shifts to hollowed out asteroids.
4) From the asteroids, colonize the Saturn system.
5) Build machine intelligence starships using Saturn resources.
6) Spread human/terrestrial DNA across the galaxy.

Gary