Stealing any item should be possible, but there should be some consequences. For instance, it is nearly inconceivable that someone could filch a large object (like a battle axe) without the owner knowing. Something like that the game should automatically turn your character to the thief and attack with the weapon in hand or something like that. An item in a backpack should be very hard to steal. For instance, if you kept your money in your backpack in a pouch (not practical if you are in a market) it would be impossible to steal withou you knowing, because they would at the very least have to cut open you pact and rummage through the contents.
Also, not very many people learn pickpocketing to a fine degree, without spending alot of time in jail at least. Perhaps that should be a penalty. If you are caught stealing, the guards don\'t pound you into the ground, they grab you and hall you off to jail for some amount of time. Anyway, some thieving skills should be hard to learn to a good level, and some should get bonuses in certain situations. For instance, if the population of a given area is high enough i.e. a crowd then pick pocketing should be much easier than otherwise. Anyway, it would be nice to see something really interesting yet semi realistic in the game