I heard from Todd that the economy is going to be much more dynamic and that we and the NPCs will have more of an impact on it. For instance when the black smith looks like he's making a sword he really is and it's added to the store inventory, and when someone farms they bring their produce to the store and sell it. Then the supply and demand changes prices as well as disposition and bartering skill. You also being able to farm or mine could help the blacksmith or farmer to effect the economy, there are supposed to be traders between towns that might bring rare goods and change the economy. If any of these npcs get killed or you burn a farm, that will change things too. For me this is all very exciting.
Source #1 http://www.escapistmagazine.com/articles/view/editorials/reviews/previews/8797-Skyrim-Preview.2
"could sabotage a town's main industry, inflating prices and reducing the availability of goods."
Source #2 Game informer's magazine which features Skyrim.
States the various abilities such as farming smithing and mining.