I've only been sporadically following this thread, and if someone may have made this point explicitly already, but anyway . . .
Regarding sneak attacking undead and constructs:
If sneak attack represents the ability to hit a "vital spot," then constructs and undead should -- except in very rare cases -- be subject to sneak attack, because D&D lacks a system to account for specific injuries and uses on hit points for a broad abstraction of them. I'll explain . . .
Presumably most constructs and undead move and act using the same general biomechanical principles as a humanoid (zombies and golems walk, meaning their "legs" bend at the "knee" and they lift their legs through movement at the "hip" and "knee" joints, etc. etc. -- zombies or golems do not "wheel" or "float" along the ground ramrod straight -- they walk.) If someone cuts off the left leg of a zombie or golem below its "knee," that zombie or golem's ability to move will be hampered, despite the fact that it is undead or a construct -- it needs the lower portion of its leg to properly move itself. Given the hinderance a legless zombie or golem would suffer, that zombie or golem is going to be a less effective combatant that a zombie or golem with both legs intact. Although it is true that, given the lack of bleeding, etc. a zombie or golem is going to be better off than a human who has just had one of their lower legs cut off, but, a zombie or golem will still be hampered by the biomechanical difficulties caused by missing a portion of a limb. The same argument could be advanced for cutting off a constucts arm at the shoulder or a zombie's arm below the elbow, etc. etc.
So, undead and constructs do, in fact, have vital spots. Given that there is no system in D&D to account for the specific injuries and effects discussed above, and that hit points represent an abstraction of all of those types of specific injuries, there is a reasonable "flavor" basis to make them susecptible to sneak attacks (the rogue cuts the zombie's arm off, or messes up the "workings" of a golems knee -- imagine the difference between shooting a bullet into the door of a car versus shooting out one its tires.) Granted, given the lack of shock, bleeding, etc. that undead and constructs will not suffer, their vital areas are perhaps less vital than a humans, but I don't think it is completely uncomprehensible from a realism standpoint to, for example, create a feat which allows a rogue to sneak attackd constructs or undead, or to (without a feat) let a rogue use half of his regular sneak attack damage when attacking such creatures.
Regarding sneak attacking undead and constructs:
If sneak attack represents the ability to hit a "vital spot," then constructs and undead should -- except in very rare cases -- be subject to sneak attack, because D&D lacks a system to account for specific injuries and uses on hit points for a broad abstraction of them. I'll explain . . .
Presumably most constructs and undead move and act using the same general biomechanical principles as a humanoid (zombies and golems walk, meaning their "legs" bend at the "knee" and they lift their legs through movement at the "hip" and "knee" joints, etc. etc. -- zombies or golems do not "wheel" or "float" along the ground ramrod straight -- they walk.) If someone cuts off the left leg of a zombie or golem below its "knee," that zombie or golem's ability to move will be hampered, despite the fact that it is undead or a construct -- it needs the lower portion of its leg to properly move itself. Given the hinderance a legless zombie or golem would suffer, that zombie or golem is going to be a less effective combatant that a zombie or golem with both legs intact. Although it is true that, given the lack of bleeding, etc. a zombie or golem is going to be better off than a human who has just had one of their lower legs cut off, but, a zombie or golem will still be hampered by the biomechanical difficulties caused by missing a portion of a limb. The same argument could be advanced for cutting off a constucts arm at the shoulder or a zombie's arm below the elbow, etc. etc.
So, undead and constructs do, in fact, have vital spots. Given that there is no system in D&D to account for the specific injuries and effects discussed above, and that hit points represent an abstraction of all of those types of specific injuries, there is a reasonable "flavor" basis to make them susecptible to sneak attacks (the rogue cuts the zombie's arm off, or messes up the "workings" of a golems knee -- imagine the difference between shooting a bullet into the door of a car versus shooting out one its tires.) Granted, given the lack of shock, bleeding, etc. that undead and constructs will not suffer, their vital areas are perhaps less vital than a humans, but I don't think it is completely uncomprehensible from a realism standpoint to, for example, create a feat which allows a rogue to sneak attackd constructs or undead, or to (without a feat) let a rogue use half of his regular sneak attack damage when attacking such creatures.