Chiming in wrote:
Speed is necessary but more likely to produce injury than mileage.
I could completely turn around what you said and say just the opposite. 100 mile weeks will only get you hurt if you are doing them wrong.
Speed is not more likely to produce injury. the vast majority of injuries suffered by distance runners are caused by overuse. It is a function of volume.
As a matter of fact, tempo runs have been more closely linked to stress fractures than speed work.