I've often wondered at those kinds of tires/bikes, and what the, heh, BIG deal is. I think in the right hands the difference could be really cool, but I don't know that I've got the right hands. Always wondered, though.
2011-08-30 16:44:35
They're to roll over terrain that other bike tires can't by dispersing the load over a wider area. Snow, sand and mud are the most popular uses. That said, they can pretty much roll over everything including potholes and cars apparently. 
I almost bought one... (There's a thread a bit below this one.) My desire to go fast over-ruled my desire to go over. There's always next year though.
2011-08-30 17:43:23
Jeff Jones uses a fat front tire rather than a suspended fork on some of MTBs. Dirt Rag is currently testing one.
2011-08-30 20:29:02
Jones makes the most beautiful bikes ever too. Droooooooool
2011-08-30 22:21:28
The front fork on that Jeff Jones bike is pretty interesting.
2011-08-31 02:50:54
Brilliant! 
2011-08-31 05:04:29
I got to ride that Jones (albeit in "normal" 29er mode, rather than in fat front mode), and it is pretty sweet. The bike looks really big, but it handles brilliantly, particularly on technical singletrack. Jones knows how to build a bike, that's fer sure.
2011-08-31 11:59:25