Sanely priced two-way trips to Mars will change the course of humanity by enabling us to colonize the solar system and perhaps ensure a longer story for all mankind. This is the most interesting thing I've read all day, and he deserves every bit of attention.
Now back to your regularly scheduled pessimism:
Humanity has a long way to go, and a change of scenery isn't going to do all that much for her. The United States of America with her vast resources and impeccable pedigree in advancing Enlightenment is operating a torture camp for political prisoners in a subtropical shithole.
What exactly happens when we send a thousand of our best and brightest and edgiest and most ambitious to live in what is essentially an submarine entombed underground for a decade? Do they live up to the Star Trek ideal? Or do they do what people in confined spaces tend to do?
Can we provide a reasonable quality of life for colonists? Beyond maintaining air pressure and food, can we provide for them spiritually and emotionally? Can we provide a -life-? Geology only gets you so far. Even on Earth it's kind of an obscure trade, and geology is about all there is to -do- on Mars.
What does a day to day life look like there? Do the children go to school? How is conflict handled? Who participates in what activities? What if there is too much to do? What if there isn't enough to do? How do you settle transplanetary custody battles when it means mommy or daddy taking the kid on a potentially lethal trip to another planet? How do you handle disease when everyone's in a thousand foot wide sphere? How do you bury people on an igneous planet? What does suicide mean for a Martian civilization?
There are a billion things to consider, and Elon has the first five thousand handled. I am delighted that we get to think about the rest now.