What about the idea that Tobi is an Oro clone like Yamato?
it would fit...
Say Oro obtained a small amount of Madara's DNA and created a clone..
1) this could be why he is "a shell of his former self"... Like Yamato is only a shell of the 1st..
So Tobi can in fact be Madara to an extent...
2) Oro wanted a sharingan right? why not 'make' one from the most powerful sharingan there was?! (yet being a clone it would have to be awakened like any other Uchiha .. Hence Oro not being able to get it from him)
3)Kabuto knew his secret ... who was Oro's right hand man?
Kabuto knew, and thus (imo) showed Tobi the real Madara...
4) IF Madara were still alive (being 100 +/- a couple, years old) Wouldn't he at least have gray hair!?! and not look like he is in his 40's.. sorry but Chakara wouldn't keep you young unless a Tsunade type tech is being used...
5) Minato went up against Madara, I think Minato would be smart enough to tell if Obito was Madara and visa versa...
6)Comparing eye techs... Kakashi and Tobi ... Kakashi can only use his tech if he activates his MS ... Tobi doesn't activate his MS (nothing has been shown other than 3 tomoe sharingan) to do his tech (that we know of)...
7) Obito just doesn't add up! so... :flaw: