For the end user and anyone that does not want a scientific answer.
Ethanol is alcohol, alcohol dries oils and rubber. When you shut your engine off the ethanol left behind starts drying the vital oils on your cylinder walls and valves. This occurs every time you shut your engine down.
For those of you that think ethanol is harmless, try running an engine on 100% ethanol. You though run 100% gasoline.
I have found that a little mmo in my gas will help combat the evaporation that occurs do to the alcohol. Gasoline is a petroleum product and ethanol is an alcoholic based product and thats why you get what they call fuel separation.
Many other good points have been made here, but remember ethanol is alcohol and alcohol dries.
I can get into burn rate, octane and btu's , but thats not the issue with ethanol.
So as far as the misconception that ethanol does not harm your engine , yes it does, slowly but surly every time you start it. The amount of wear may be minuscule, but it add up over the years.