Re: Who do you think Tobi is?
I personally believe that Tobi is Madara, but the current Madara is in fact Izuna Uchiha.
Basically Izuna took his brothers eyes and pretended to be him, because he was jealous and wanted to take over the Clan, they were of equal power, and brothers so it was not impossible for him to achieve. This is at the point where we see "Madara's" role as head of the clan move from a leader to an extremist outcast. The real Madara now without his eyes, runs off pretty quick to live in solitude and bide his time, collecting Uchiha eyes to try and get his original power back, and Izuna goes off pretending to be his brother and loses to Hashirama.
There are a few holes i know, but this theory was much more sound a few weeks ago when i thought of it, but recent evens have made me reconsider.
This is just my opinion atm, it makes sense to me, even if dont explain it well.