You like my idea about MS. I'm flattered. But I believe Itachi did kill his best friend to get it. My idea about MS was that there are many ways to achieve it, sort of like how Buddhists believe there are many paths to achieveing Nirvana. It's just that you have to realize some inner truth to do it. For Itachi, killing Shisui was like lifting a veil that was covering the answer so to speak. (Really philosophical for a simple shounen manga I know). I just thought of it that way because simply killing a friend for the power seems too simple.
Anyways, as to why Itachi killed his clan. Itachi was already very strong at the time he killed his clan, possibly stronger than any Uchiha ever known, but it also seems that he felt the clan (and Konoha to a lesser extent) was holding him back. There are hints in his dialouge about this. Like you said, he resented his dad for always pressuring him about the importance of the Uchiha clan. So he felt that he needed to cut those bonds and started with Shusui. The reason Itachi told Sasuke to kill Naruto is because Sasuke is similar to himself, and he believed that Sasuke killing his best friend would achieve the same effect. So yes, he did mean that literally though he might have understood the meaning behind it better. I believe his entrance into Akatsuki pushed him to finally to do the deed, but the hatred had already been there for a long time.
As for Kakashi's MS. After the lengthy discussion with others, I had to resign myself to the possibilty that he simply copied it from Itachi, though I'm not yet convinced that's the case.
BTW, couldn't this have gone in the already existing Itachi thread? Or did you
really want to make sure people read it?
