Lily's soul quite literally got in the way of the soul fragment that was supposed to go in an object?
Did Harry survive the AK because Lily gave Harry her soul at the moment of his "death"? Is that what is running through Harry's veins? Is that why Harry has Lily's eyes, eyes that are the window to the soul?
Now, this is not a Horcrux per se, because Lily did not kill in order to split her soul. Rather, she made a sacrifice of her entire soul in order to save Harry. It is horcrux-like, because we now have a soul residing in a new receptacle.
This theme has been hinted on in numerous threads, but I thought I'd pull it out and let you talk amongst yourselves.