well when tobi showed sasuke his past madara took only one eye from izuna uchiha i bet its izuna and not madara other wise it would be worse to see madara getting revived by kabuto if hes tobi there are many other clues wich it could be izuna or shusui uchiha
I think that Tobi is realy Uchiha Madara, but a clone that the real Madara created from his and Hokage's cells. It's not the first time we see cloning from Hashirama's cells in Naruto(see Yamato, Zetsu, Zetsu army and Hashirama flower clone) We know that Tobi has Hashirama's cells, and we have seen that he is not exactly very... human. Check 2:30
And for some strange reason, when we saw his other Sharingan, everything exept his Sharingan is darkened:
So is Tobi realy a human?
Moving ahead, from Madara's words, we can see that there was some plan between Tobi and Madara, possibly to revive Madara with Nagato's Rinnengan.
Madara knew he will be resureccted, but then he is surprised that it was "Impure World Resurrection", rather than Nagato's "Outer Path: Samsara of Heavenly Life Technique".
Here, from Madara's words, we can see that when saying "This is his doing" he possibly reffers to Tobi, and then Kabuto tells him "I'm Kabuto... his assistant" who reffers to Tobi as well.
Also, before Tobi said Konan that it was he who gave Nagato's Rinnengan and also gave Yahiko the idea to create Akatsuki. Another thing that Tobi said before is that he is a weakened version of his previously self, meaning Madara from the old times.
So maybe the plan was like this: Madara created Tobi from Hashirama's cells, then Madara or Tobi somehow gave Nagato the Rinnengan, and the idea to Yahiko to create Akatsuki. Tobi controlls the Akatsuki behind the scenes, collects the Bijuu, resurrects Madara, who died from his battle with Hashirama, or from something else, trough Nagato, and either Tobi or Madara become the Jinchuriki of the Juubi and rules the world. What do you guys think?
Lol even though i just realised this i still don't think tobi can be obito. But the thing i noticed is start at the "o" in tobi and keep reading the name until u get to the "o" again and it spells obito lol. But thats impossible because as u can see from pats post that guy has both of his eyes lol. Ummm but what I do think is that the imposter behind the mask has to be someone of close relation Madara only because as u can see he has wrinkles in his eyes which means that he is old. Don't forget Madara and Hashirama lived about 80 years ago which isn't that long, so I would assume it's either a relative (not the brother) or someone important who had something to do with establishing konoha and the new ninja world.
What!? This red eye was just a genjutsu to KO the Rain ninjas...
NNNNOOOOOOOOOOOOOOOOO
his red eye was about to destroy them when naruto quickly beat up the rain ninjas the author has left many hints about the plot that's why he adds information that makes no sense