I think my only issue that I have with this is, well, the technology that we have currently seems extremely, extremely impractical for an endeavor like colonizing Mars. I'm all for colonizing planets and exploring space and all that jazz, but... the technology for terraforming on a scale that you'd have to accomplish to make someplace like Mars inhabitable, as well as continually inhabitable (because there will have to be some kind of accommodation for Mars's atmosphere, its distance from the sun, etc. And if the solution was making some kind of large dome or something of that sort, then you have to consider the scale of such an installation, with people that probably don't have prior construction experience, in an atmosphere that we've never had live tests on to see if the structure wouldn't immediately collapse in upon itself. And, again, this has to somehow be able to sustain and produce food by itself, because without any way to achieve Faster Than Light travel (or at least some kind of reasonable travel distance between Earth and Mars), any colonization attempt is going to be woefully destroyed by this little thing called finite supplies.
I mean, good luck to them and I personally hope that we can pull off this colonization, in the future or even right now, but right now this seems like a huge shot in the dark without a lot of forethought. Now, I'm not assuming that I'm smarter than NASA and that they hadn't considered these issues before even making the Mars One mission as popular as it is... but seriously, I don't see this working with the hand we're dealt right now.