I too am one of the 2012 DNF's. I had a fall on the Prologue, I cut open my head but continued, or so I am told, I can not remember riding at all. Went to hospital and got 14 stitches to my face. I convinced the race doctor that I was fit to continue. I finished stage 1, vomiting for 70 km and my head killing me. Race doctor gave me one look and withdrew me. I am back home with concussion and still feeling terrible. My eye is swollen shut and looking worse each day. I accept that I could not have continued. I am absolutely shattered. What could I have done better? Nothing, my preparation was spot on, I know I was ready. What now? Will I go back? Yes I will. For now just want to get over the concussion and then plan again from scratch.