A little blur is not a bad thing, and in some cases is actually important for the picture. To pick a small point, I am not so sure that this famous Capa D-Day blur came about when he was taking the picture. I seem to remember something about his negatives being overheated during drying, causing the emulsion to melt and move. Those particular pictures would have been far more clear, and far more meaningful, if they had not been damaged during processing. I suspect that Capa would have preferred it that way.