well am sure that tobi isnt orochimaru because remember when danzo was fighting sasuke and tobi relized that danzo had met with orochimaru. he said *damn u orochimaru * . why would he say that if he was orochimaru. but i do believe that orochimaru had something to do with tobi. because if u notice , tobi has that same body has orochimaru. look at the chapter where he fights with minato ( naruto's dad ) and his hand comes off after minato's attack. he has been keeping himself alive using the same method as orochimaru. probably changing bodies also. so all tobi is , is an uchiha that has been keeping himself alive for a long time by experients from orochimaru. thats why sasuke says * the one who knows everything * . orochimaru has been alive longer than u guys think. he knows all about the hokages and past events because he has been changing bodies for years to stay alive up until now.