If I wear shoes for the first two miles, I can go barefoot for two miles if it's wet and in the thirties or if it's dry and in the twenties. The rougher the surface the less tolerable the cold is.
A study was recently published that took a look at the effect of running shoes on the body. The verdict: Bad.
After you get through the statistics and charts and ankle dorsiflexion torque and knee varus torque language, you find this quote.
The design of current running shoes, with various heel-cushioning strategies and technologies to increase medial support to control foot pronation, has become widely accepted as the industry standard. However there is no clinical evidence to support that this design is optimal to promote the long-term health of runners. In fact, the rate of running-related injury in distance runners has not changed dramatically despite advances in footwear design technologies.
It's not the definitive verdict nor the last word. But it's a good point.