I'm not a fan of being able to steal highly valuable items that are several feet across from of a NPC's person. I'm all for players being able to do as they like in RPGs but I'm also for it being realistic, and I don't for a second believe even a talented theif could walk into a store and take large elite items from a shopkeeper without being caught.
So basically there should be no way for thieves to steal good items? Then what's he point in even being a thief? And for that matter, in what kind of alternate reality is having shop keepers' inventory magically sealed in a place not physically accessable at all? Because when I think "realism" in this regard, that is NOT what I think of at all, in fact, hearing "realism" makes me think of having the items in a place where they ARE accessable, it wouldn't necessarily be easy for someone to get them without consent, actually, it would be quite realistic for merchants to take certain precautions to prevent their items from being stealing, but that should be obvious even if you don't bring realism into the matter, because there's no challenge in just walking in and taking items without any effort, and therefore, it would be boring to do so.
And no one said it should be easy to steal, just that it should exist in a place where it IS potentially possible to get it. And I agree, what's the point in being a thief if all the good items are magically sealed in places I can't possibly get to without using the console? Absolutely none, in Oblivion, I felt that the mechanics of thieving was considerably improved over Morrowind, but at the same time, being a thief was completely unrewarding, except for stealing things as part of a quest, because Bethesda apparently decided that you shouldn't be able to steal anything even remotely worthwhile, thus, our thieves get to steal such amazing items as calipers and yarn.
The stock merchants carry should be well guarded, but it should be possible to steal, not easy to do so at all, but possible, to do otherwise would be like not letting warriors find good loot in dungeons, either way, it serves to remove the reward from role-playing your particular character archetype, therefore making playing doing so entirely pointless.