As Buzz points out, one of the biggest problem with the current space plans is the "we'll go there, and be back in time for tea" attitude. I.e. the requirement that anyone going to the Moon, Mars etc. be able to return.

We should be aiming for colonizing space with one-way trips and subsequent supply drops. The colonies should aim to become as self-sustainable as possible using robotic factories to mine and produce what they need on-location.