A lot of people often ask me something like, "If technique is so important, then why do so many world class runners have bad technique?"
First of all, this is mostly just true of distance runners. Middle distance runners generally have good technique, and sprinters almost always have very good technique. But to answer the question, in distance running the over-riding factor for performance is physiology. The athlete's VO2max and Lactate Threshold are far more important than technique when it come to performance.
So then why is technique important? First, it prevents injury, allowing for more uninterrupted training time, which hopefully results in faster performances later on. Second, it allows the athlete to live up to his or her full potential, and at elite levels of competition this will make a big difference. The African runners, who have dominated distance running for so long, have no physiological or anatomical difference that can account for their superior performances. However, they do generally run with much better technique, and that coupled with training very hard probably helps them to out-perform equally talented runners from the West.
Below is a video of Alberto Salazar, who was probably one of the most talented distance runners during the 1980s. His technique is clearly not very good. His career was probably cut short for two reasons. The toll his poor technique was taking on his body, coupled with the fact that he began to obsessively train with extremely high mileage of around 200 miles per week.