Sin and Punishment?
The beginning of today's passage deals with an issue that has been around probably as long as there have been people on the earth. As Ecclesiastes says many times, "There is nothing new under the sun."
So the question is this: why people suffer, is it because they are being punished for sin? Jesus deals with two different situations:
"In the discussion of the two tragedies in verses 1–5, the question emerges whether a worse level of sin causes a person to suffer a special judgment, either in being the victim in a series of events or in being the victim of a natural catastrophe. The temple massacre of the Galileans whose blood Pilate mixed with Jewish sacrifices raised the question whether God was exercising a special act of judgment against them. The collapse of a tower at Siloam that killed eighteen was a natural catastrophe—one of those things that just happens. But here the question also becomes, “Did God judge them for excessive sin?” In both cases the question is the same: Is God giving back to people what they deserved?" 
More personally, it's easy for us to feel this way (though we might not verbalize it) about people we know. "It's sad that he has cancer, but he kind of deserves it for the way he lives." Again, we'd never say it, but sometimes we might think it. This obviously has a huge application in our family as my wife Rachel is in a wheelchair. She's talked many times about her experiences and what God brought her through. In one telling of her story, she put her original thoughts/feelings after the car accident this way:
"This is all my fault! God’s punishing me because I cheated on those homework assignments at school. God blesses those who obey and Him and punishes those who disobey Him. This is all because I’m such a horrible person and God’s trying to wake me up! God, please don’t punish my family for my mistakes! If you take care of my family then I promise I’ll never cheat again! Please just help everyone be alright and please help my legs to get over this and start working again soon!"
A lot of us have this subtle, unspoken deal with God: "I'll be a good person and you keep things going good in my life." If something bad happens, the whole system falls apart - either it's that God is not good and hasn't kept His end of the bargain, or that we have messed up in some way. Rachel went through both of those feelings before realizing that the "deal" doesn't exist and that God has other purposes in suffering. She's talked a lot about this before (even in our church), but if you have questions, please ask her! God uses suffering, just like everything else, to work His good purposes in our lives.
We might not always think these "bargain" ideas straight out; we won't necessarily believe in a prosperity Gospel where if we are good Christians God will bless us with money. BUT...we do it in small ways. "I'm having a bad day today...OH! I know! I didn't read my Bible today" or "Things have been bad lately. I need to deal with ________ sin in my life." No! You need to deal with that sin because it is sinful and you are being sanctified by God, not so God will "make things better" in your life! It's a subtle line of thinking that can have DISASTROUS and SOUL-KILLING consequences. It makes fundamental false assumptions both about ourselves and about God and usually ends up with God getting the blame when the problem is our twisted thinking. This is a HUGE topic that we don't have time to fully deal with here, but we'll be dealing with these things in-depth in the coming months. Later in the New Testament some of the epistles deal a lot with the issue of suffering and its purposes. Additionally, when I finish up my current sermon series on Colossians I'll be doing a series on suffering. The point is: I know there are a lot of questions. Feel free to ask them. We'll also be dealing with these issues and many more in the coming months.
This is a hugely important topic, but we've gotten a little off track. Going back to our passage for today: Jesus understands the purpose the people have in bringing up these tragedies. What is His response?
"Jesus responds by changing the import of the question. The reason such events are so tragic is that they expose our mortality. Death exists in a fallen world, and nothing exposes our mortality more than when death comes suddenly and unexpectedly, cutting short a life that had the potential to be much fuller. Jesus argues that what should be contemplated is not the cutting short of these particular lives, but the fact that life terminates. This raises an even more basic question, what comes after that? How does one prevent the end from being the ultimate end? Jesus has taken a question about mortality and made it a question about the possibility of eternal punishment. So he urges the people to repent, without which all will perish—only in a death that is more than a mere loss of mortality. His point is that with death comes a decisive encounter with God, one that does deal with sin. Whether one is a little sinner or a big one, repentance now is the only way to survive that coming encounter."  (bolding mine)
The point: don't worry about others. Worry about yourself! You don't know anything about those people and God's purposes in what happened to them. Consider yourself and deal with your sin, not out fear of punishment, but to please and glorify God!
 Ibid. 365-366.