A Marathon Without Training

Running a marathon is on my list-of-things-to-do-before-I-die. Over the past year, I've made running a regular part of my life, and I've normally gone on one or two runs a week. This culminated in my participation in a half-marathon in Albacete, but that was just a mid-level goal, not the final objective. Although sometimes I've had convenient excuses to not run (no audiobooks to listen to, temperature too hot or too cold, my work hours don't allow it), since the half marathon I've tried to continue running weekly. My running in Murcia is much less than my running in Albacete was, but today I came across something that made me question whether I even need to spend so much of my time running (according to Sports Tracker I've spent nearly 70 hours running over the past year, an amount of time that would get me an excellent base in a new language or some other skill): Sean Ogle, a mobile travel guy, ran a marathon with practically no training.

What?!?!

I don't doubt that it can occur, but although I am tempted to immediately sign up for the next marathon in my area, but I am dubious of the soundness of planning to run a marathon with such limited training. What about injuries? What would the physical consequences be of running a marathon without training properly for it? It is possible that I am in better condition to run a marathon now than Sean Ogle was when he ran his marathon, but I am still not completely sold on the idea that I should enter a marathon without far more significant physical preparation. I am tempted though...