i'm also thinking that Kakashi's sharingan is an implant. anyone ever think that after Itachi wiped out the entire Uchiha Clan including his own family, except Sasuke who ran away, that the Hidden Leaf Village would want to loose the military power that the Uchiha Clan represented. and that could lead to Hokage and the other village leaders to try and salvage whatever was left of their special ability, the Sharingan, and regain it in whatever form they could. this meaning finding somebody with the abilities and strength to use the Sharingan.