I really think it's possible there the same person

1. They have the same hair style

2. Jiraiya told Tsunade to watch out for root because Jiraiya suspects Danzo being up to no good and if so by now he would have killed Tsunade where is Danzo at?

3. Tobi has one sharingan eye the right eye and Danzo has one regular eye the left eye could Danzo be hiding a sharingan?

4. In one chapter Tobi said something about Sasuke remaining a snake or sheding his skin and becoming a hawk.

5. Why doe's Tobi have an interist for seing Sasuke's develepmont?

6. Sai for some reason want's to kill Sasuke possibly because he want's to give his sharingan to Danzo?

7. Why else would Tobi sacrifice Deidara maybe to test out Sasuke's power?

8. Tobi said: The sharingan's true power... My power Uchiha Madara's power possibly cause he has an interist for getting Madara's power?

9. Tobi wear's medical pins on his arms and Danzo has lost an arm.

These are to show people the possibility of Tobi being Danzo but note: This is just a theory doesn't mean it's true.