Re: Madara and Tobi the two people behind the mask !
Still haven't found the page I was looking for. Will look tomorrow.
But, Itachi rigged Sasuke's sharingan to react to Madara's sharingan (or actually Tobi's sharingan, but he thought Tobi was Madara). This would seem to imply that, at the very least, Tobi has the same eyes as the masked man that Itachi met with prior to the massacre. I guess it's possible that Itachi rigged it to react to any sharingan, but would've happened if Sasuke was a good little boy and went back to Konoha? He'd be fighting along side Kakashi, who would bust out his sharingan, and Sasuke would unwittingly fire off an amaterasu, killing Kakashi => Sasuke is a criminal once again. Itachi's not stupid enough to make such a mistake.