I generally run fairly tight on my road bike pedals, but they aren't SPD. All it takes is one or two accidental unclips during an all out sprint, and you will see why increasing the tension can be a good thing. This is especially true if you have the multi-release cleats. That being said, before I switched to Crank Brothers on my mountain bike, I kept those SPD pedals fairly loose because I wasn't doing any major sprinting and liked the idea of being able to unclip in a hurry.