I am rather in favor of the following hypothesis concerning Orochimaru:
Orochimaru and Danzo reportedly experiences together and concludes that the power lay in the possession of the sharingan.
A first test is done on the left eye Danzo (you can see that his sharingan is bizarre and not exeptionnel)
transplantation with partially missing, Orochimaru is said that it is better carrement take possession of the body of an Uchiwa for better performance of the sharingan.
He returned in the akatsuki but is not itachi, so he falls back on Sasuke.
Hence, too, is interested in Danzo notes Orochimaru.
and where danzo have take the eye for the test ? when itachi have kill all uchiha

? who have ask itachi for kill all uchiha ? DANZO
For me it is the most likely solution.
This post was edited by Guivolvo1177 on Jul 9 2009 10:54am