It seems appropriate right after Easter to talk little about Pontius Pilate who played a central role in the events surrounding the trial and crucifixion of Jesus. Surprisingly (to me) this is not the first time we hear about Pilate. Witness the following account from Luke during the ministry of Jesus:
At that very time there were some present who told [Jesus] about the Galileans whose blood Pilate had mingled with their sacrifices. He asked them, “Do you think that because these Galileans suffered in this way they were worse sinners than all other Galileans? No, I tell you; but unless you repent, you will all perish as they did. Or those eighteen who were killed when the tower of Siloam fell on them—do you think that they were worse offenders than all the others living in Jerusalem? No, I tell you; but unless you repent, you will all perish just as they did.” Luke 13:1-5
This parable is clearly intended to bring us to repentance. The word translated as 'repentance' is the Greek word (metanoia), "after/behind one's mind", or in other words to help us ‘change our mind’ about our sinful actions. For many years this parable stuck in my mind because Jesus’ response to his listeners clearly avoids a hierarchy of sins. This led me to question ‘why does the Church insist on categorizing sins such as venial and mortal sins?’ The Ten Commandments already provides Christians with a list or specific sins to be avoided. And, if you are a Orthodox Jew the Bible additionally provides a nearly exhaustive list of 613 laws or precepts to be rigorously observed. ‘Other lists of sins are found in the writings of the prophets. In the New Testament we find similar lists of sins. In his first epistle to the Corinthians, Paul lists those who will not inherit the Kingdom of God: ". . . people of immoral lives, idolaters, adulterers, catamites, sodomites, thieves, usurers, drunkards, slanderers and swindlers . . ," Note: our sins will indeed keep us from the Kingdom of God until we seek repentance. I recall a priest at a retreat reminding us that most of us are frequently ‘in and out’ of the Kingdom in a single day’. 
Regarding the question why did the Church create a hierarchy of sins; especially in light of Jesus’ avoidance of the same? Noted Catholic historian Professor Thomas Bokenkotter speaking in 1992 provides the following important background and theological progress on this exact question:
“One of the concerns regarding sins has always been their degree of seriousness. For Catholics, this concern was intensified by the mandate of the Council of Trent that all mortal sins be confessed in detail. This resulted in an unhealthy preoccupation with trying to define accurately and even quantitatively the boundary between mortal and venial sin. Such a preoccupation was certainly foreign to the spirit of the Bible, which spoke of sin not in terms of mortal and venial, but of fundamental option or conversion.
But under the influence of legalism and the rigorism associated especially with the Jansenists and also the advent of the exact sciences with their obsession with measurement, Catholic moralists of the seventeenth and eighteenth centuries often emphasized the quantitative and objective aspects of sin. The classic example of this kind of thinking is found in the Catholic theologians who taught that the theft of one to five ears of grain from a rich man's harvest was no sin; theft of from six to ten ears was a venial sin, while any amount beyond that constituted a mortal sin. Older Catholics today will recall how extreme this tendency could become in the pre-Vatican II Church. A venial sin, for instance, was committed by voluntarily missing the first part or last part of the Mass (before the Gospel or after the Communion), but to miss both of these parts or the Consecration alone would be mortal. In matters sexual, this led to a dissecting of the human anatomy as to which parts, if touched, provided zones of mortal and venial sin, etc. Many Catholics brought up in this system still suffer from scrupulosity, being frequently tormented with doubts about whether a particular action or even thought was a mortal sin or not.
The quantitative and objective approach to mortal sin has largely been abandoned by Catholic theologians today, who prefer to think of mortal sin in terms of what they call the fundamental option.”
"Fundamental option" refers to a theory of morals according to which each person gradually develops (their conscience) in a basic orientation of his or her life, either for or against God. This orientation is directed by a person’s actions. John Paul II is quoted as saying “Scripture sees the fundamental option as a genuine choice of freedom and links that choice profoundly to particular acts. By his fundamental choice, man is capable of giving his life direction and of progressing, with the help of grace, towards his end, following God’s call (no. 67).
While Bokenkotter states that Catholic theologians may have abandoned the quantitative and objective approach he was speaking more than twenty years ago and today 2011 the Church under Pope Benedict XVI wants to return to a more rigorous style of defining and interpreting sins.
It would seem to this blogger that a healthier approach to understanding and dealing with our sins would be to seek council available 24/7 directly from our advocate the Holy Spirit. It is He who will reveal our sins before we even approach the Sacrament of Reconciliation. The Jesuits have been teaching this method for centuries under the name ‘Examination of Conscience’.