To quote from the article: "[Planetary Resources] want to make sure there are available resources in place to ensure a permanent future in space." Our future, eventually, is in space. Whether from global warming, resource exhaustion, or nuclear war, Earth will eventually not be enough. When that day comes, we will be glad some billionaires chose to spend their money on space expansion, instead of building/buying shiny new toys, or hookers and blow.
If we eff up this world we don't deserve to get off. At some point we have to to take a hard look in the mirror and fix ourselves rather than just spreading our misery across the galaxy.