Phil Bowermaster has some thoughts on what I think is actually quite a likely scenario for the first human on Mars. It won't be done by NASA, though, or likely any government space agency. They simply can't afford to take the risk when it's funded by taxpayers, as we've seen when the nation gets unreasonably hysterical over astronaut deaths. It will be a privately funded expedition, which will be able to do so without the intrusion of politics.
And of course, this will be more in the nature of such exploration. After all, the vast majority of polar exploration (e.g., Peary, Scott, Amundsen, Shackleton) was privately funded. Once we get the cost of access to orbit down, and establish an orbital fueling infrastructure, it will be quite feasible to raise the money for private adventures such as this.
Sadly, NASA is contributing almost nothing to those goals, instead spending billions developing expensive government-owned/operated launch vehicles and capsules that will likely become obsolete before they first fly.
Sending just one man is a bad idea. Send a crew of 4. They are committed to stay. Send an inflatable habitat and supplies landed via the airbag method. Repeat: another crew, more supplies. They connect their habitats to one another like ISS modules. Repeat. Repeat. They're still living off supplies from Earth. Send inflatable greenhouses so they can grow food. Send solar panels and batteries. Send a small nuclear reactor. Send specialized equipment like Mars buggies, backhoes, well drillers, water processors, whatever. They get dropped in the area, dragged back to the base camp and set up. The process will have to continue at least until the colony is self-sufficient, because you can't let these people die on television.
I think that the transformation of humans into a space faring civilization will look a lot like the story/book the Rocket Company.
http://www.hobbyspace.com/AAdmin/archive/SpecialTopics/RocketCom/titlePage.html
Admittedly, one sounds like a thin crew, but the multiples add up quickly as you add crew, their supplies, and the propellant required to take them there.
Doesn't make it impossible, just more than 4X heavier.
It seems to me it would be hard to justify sending just one person. The benefit vs. delta V necessary to send another person would more than justify it. Sure, it would shorten the time before the next necessary resupply. I just think the risk of losing the entire mission, not to mention the first astronaut to step on mars, all due to a broken ankle/leg or other appendage that with two people wouldn't end in mission and astronaut death.
Something we might not consider a very big deal here on earth can easily mean death and failure when you're all alone.
I might not mind dying on another planet if it meant establishing enough infrastructure for others to follow, but I'd be pretty pissed if I broke my leg stepping out of my lander and accomplished nothing before my supplies ran out.
Sending 4 to the Moon is, by some, called just more "flags and footprints", but 1 to Mars is "exploration"?
Now if we were talking about sending 2 couples to Mars on a one way trip that would be colonization, on a tiny scale of course.
Of course, if Mars were to be quarantined (and by whom?), as spaceflight matures and becomes more accessable for other reasons, enforcing such a ban should be interesting...
Doesn't anyone remember Hank Searls' novel The Pilgrim Project?