I was at the mtb worldcup at the weekend and got talking to a guy who does snow/sand dune biking .He has a surly with enormous tyres and special wheels .Front has a single sprocket for swapping over in an emergency if freehub packs in.anyways he has a blog which is worth alook for the novelty factor if nowt else.
coastkid.blogspot.com
he is a regular on singletrack world – stays in East Lothian – he postsup some amazing pictures of epic beach rides – well impressive indeed