You can find the original article (not the io9 commentary) over on TheOneRing.net. I posted it here back about the time it first came out and I think it's a pretty interesting read.

http://www.theonering.net/torwp/2013/01/03/67872-radagasts-racing-rhosgobel-rabbits-a-recreational-musher-looks-at-the-realities-of-bunny-sledding/

Now that real BIG bunny...those things are just disturbing in my opinion. As mentioned above, in our reality they just get too slow at that size but I do think it gives good argument that in Middle Earth this just might work.

A friend that got the BR/DVD combo of the Hobbit passed on the DVD to me so I've watched it a couple times while waiting for the Extended. Although I can admit to finding the whole Sled "in character" and amusing I'm still a little disappointed on how it was pulled off for the chase scene. It looked fine in the forest but doesn't seem to hold up as well for the distant views. It seems to 'slide' along without enough respect to the terrain or physics. But I always have pretty high expectations for effects. Also, he was supposed to be leading the hunters AWAY from the Company. I know you can see a small group of riders come in to cut him off early but I can't believe he couldn't avoid just running around in a big circle around them. Maybe he did drink a little too much mushroom tea.