User blog comment:The severus snape/Noticed something the other day.../@comment-117.217.133.248-20120818143857

Its simple. A horcrux is detsroyed when the vessel is become irrepareably broke. The booke was destroyed, so was the cup and locket. Harry, being a living creature, had to die to be "Destroyed". Same with Nagini. The horcrux was destroyed when she was killed. Voldemort's killing curse was supposed to kill. He "died", in that he left the mortal wold, but returned thanks to his link to Voldemort.