Yes. A person has admitted to walking to win distance challenges.
It's.......winning is above all else.
Some people, for various reasons, can't run.
Nike+ adds a bit more motivation for them too.
They should be encouraged to join up with Nike+ and keep walking.
Walking is their regular workout and is very beneficial for them.
I'm amused when a person can run 5k under 15 minutes but has a Nike+ career average around 10 minutes per kilometre due to the amount of walking done to increase distance for challenges.
There are posts through the various nike+ threads that can give you the details.
I'm guilty of walking also. In march or april I walked about 10KM on a treadmill as part of a training program, while using nike+. I didn't like it. It was doing nothing for me. Since then all Nike+ Kilometres have been run.
Running suits me.........I'm hooked on the endorphins

I'm running because it gives me mental and physical challenges.