WiB, okay, fair enough. Looking back to the original post it was about people who had walked 'the majority' of the race, some of whom would have planned to. But if they'd planned to they'd probably be people who couldn't run for whatever reason, and might therefore find it harder to walk than you or I might find it to run. And if they hadn't planned to, they'd have started off running and then walked, and the walking would be harder than normal walking.
Having thought about it, I've decided the easiest thing for a moderately well-trained person would be to jog the whole thing at recovery pace. Less time on feet than walking, less effort than running.
The moral of the story appears to be that it will hurt if you go far enough without training, regardless of how you do it?