could danzo b madara
Danzo could also be Madara Uchiha, Tobi has bolts on the same arm that Danzo has covered up. Similar hair styles. Not only that, he and Madara share the same hate for the First, Second, and Third Hokage's Teachings and Philosophy. Plus Madara hates the Senju clan, and the first and second were both Senju. Danzo also despises Tsunade for being the Grand-daughter of the First. Danzo also has the same eye covered up that Madara has his Sharingan. Kisame's revelation of Madara being Mizukage offers more support to this theory as Danzo's Root is said to use extremely similar methods to Kirigakure earlier on, the education that led to the village being referred to as the Village in the Bloody Mist.
Danzo is also said to be incredibly handsome when he was younger (probably as handsome as Kakashi seems to be when his mask comes off) because Tsunade and Shizune look through old photo albums in the extra at the end of shippuden episode 64 (Middle of the hour special).
its is possible that during the war or the accident danzo lost his arm he engaged or awakened a split personality
he did have secrets from itachi
but this is just an itachi
danzo could also b a student of madra
this is only a theory
how come know one is saying anything i want reps dammit