I'm convinced that Tobi is Kagami.
1. Tobi was familiar with Danzo's seal jutsus before he used them. (Kagami was in danzo's squad during the first shinobi war)
2. Kagami's death was never actually seen.
3. He was also an Uchiha as well :O This shit cray! Obito was still a child when Tobi first showed himself back when he fought Minato.