Originally posted by King KandyYou know..if Madara, and his brother were the first to awaken MS, and they were probably in there teens at the time, you have to wonder how the Uchiha Clan wasn't extremely small in the ten years before merging with Konoha, and how that in the 60 years of Konoha only Itachi ever had MS when a lot of Uchiha's were getting it.
First off, here it's stated that it only works on clansmen... it also states that many have killed eachother for their eyes, but you'll probably want something more explicit...http://www.onemanga.com/Naruto/386/09/
Here it's flat-out stated that tons of uchiha have killed eachother for EMS:
http://www.onemanga.com/Naruto/386/13/
As for why only Madara got immortality, there's nothing to say except that it is simply not known at the moment.