I'll throw another log on the fire here just to make it interesting. If you walk a marathon are you still a marathoner?
Windwalker

Why not? It's not as though a walked marathon has fewer miles or anything. Heck, IMO, it's easier to run the distance rather than walk it - I'm done earlier, off my feet earlier, the aid stations are better stocked earlier in the day, the crowd support is stronger earlier in the day, and the weather is often nicer. I run so I can finish earlier, because I am a wuss.
I often tell novice runners about a story I heard, where a reporter managed to snag the DLF (dead last finisher) and the first place runner of a marathon in a post-race interview. The winner had showered, gotten food and a massage, and the DLF was still in running clothes, drenched in sweat and caked with salt.
The reporter says "Winner, you finished this marathon in two hours, twelve minutes. And DLF, you finished the same course in seven hours."
The DLF looked at the winner in amazement and said "You were able to run the whole race in only two hours?"
And the winner looked at the DLF and said, in equal amazement, "You were able to keep moving for seven hours?"