dmallind raises an interesting concern, but one that has not been anywhere near the center of theological thought for a long time. Theology has moved a long way from the ancient or even the modern juridical concern about sin. While it is true that some churches, basically the Roman Catholic and Protestant fundamentalists, still seem to center on obedience, and the accompanying guilt, progressive religion has moved in another direction. This direction was instigated by Jesus who held that all the commandments could be summed up in loving God and loving each other. So right living moved beyond obedience to law, to an ethical imperative. Far before that, the prophet Micah held, in the face of the commandment keepers, that religion could be reduced to doing justice, loving kindness and walking humbly with God.
This notion of right living has come not only from and through religion, but in all sorts of non-religious secular perspectives, because this ethical system is deeply rooted in the heart of reality. Religion has only offered a way to access what is universally true. It not only has to do with how we related to one another, but how we care for the earth, the preservation of peace and harmony between nations and even ideologically diverse perspectives. It has basic implications for how we deal with the outsiders, the "non-persons", the disabled, the poor, the left out. Those are the people Jesus included. This personal action simply followed his articulated ethical stance.
Perhaps sin is to live outside this ethical imperative. If you want the full treatment of this notion read Emmanuel Kant and his categorical imperative. Put simply, it is acting as if were your action to become universally accepted, it would eventuate in a better world. In every world religion the corollary comes in words like, "do to others as you would want others to do to you." These corollaries are exactly what Jesus meant when he summed up the list of commandments.
Most contemporary religions discourse deals with this ethical imperative, not sin.