Is Itachi responsible for killing his Clan.
Now I'm not sold on the Madara is Tobi or Tobi is Obito yet partially b\c of the translation which really doesn't specify whether he is saying he has inherited the power of Madara or if he is Madara himself. That said since the last sharingan has finally been found it makes me wonder if Itachi was being controlled by Tobi's genjutsu while he slaughtered his clan. Itachi's plan to test his own limits through Sasuke could actually be Tobi's intention to see whether Itachi or Sasuke would eventually become the most skilled Uchiha. I don't have the specific chapters but seeing as how Itachi(or atleast I think it was Itachi) knew of a another sharingan besides his and Sasuke's and the fact that every time someone mentions the fact that Itachi killed his clan he never really responds most recently in the last chapter when Kisame mentions the fact that he is the last one left I always found it odd that he never responds even though of his bland personality. Tobi may have eventually revealed himself to Itachi and recruited him. It is also possible that Tobi didn't use genjutsu and recruited Itachi willingly. Of course I'm not sold on this either I just find it odd that Itachi could be kept so easily in the dark.