@Naruto vs Goku: good points, but Fukaku(not Fugaku lol) does have a chance of being the masked Tobi. About your nobody having enough knowledge argument, well Tobi speaks of even the Sage of the 6 paths, his 2 sons and all that happened between them, which was waaaay before Madara's time......so even if Tobi=Madara, how does Madara even know all this? By having MS? Its just as likely that Fukaku activated it too by killing off a close relative and then read it off the uchiha tablets, which is what Madara would also have to do too.
But more importantly, Tobi has space time, and its not known if the original Madara did. Hashirama never used space time, but the 2nd and the 4th hokage's did. Any uchiha with sharingan can copy techniques perfectly, and can even work to improve them, but they have to see the tech in action first.
Madara did'nt have the opportunity to do that as probably no one in his time used time space nin techs. But Fukasaku probably grew up hearing of the exploits of the 2nd hokage and minato and might have seen them in action and copied their abilities and improved them, just like first Oro and then Kabuto copied the 2nd's IWR jutsu. It might be a stretch, but then how do you explain Tobi having space time...?
@ BarBoBot: You're missing one very critical point. How does the real Madara now know of Nagato...?Nagato, who was a child of about age 6 or so during the 3rd great ninja war, when the 3rd was hokage and it had been ages since the valley of the end battle. Madara wore the same clothes as he did when he fought the 1st when he was ressurrected, so this leads to an inescapable conclusion:
Although it may very well be that Tobi and Madara are 2 distinct beings, they are almost certainly connected, and its possible they may have had some form of communication, perhaps like how Minato communicated with Naruto.
What do you 2 think?