And DO NOT give in to the temptation that seduced Pat Robertson. He is JUST LIKE the disciples in John 9, who stand there looking at the man born blind and begin discussing the causes of his circumstance. I see them nodding, pursing their lips, rubbing their beards as they ponder the existential dimensions of original or actual sin...
Jesus says only that the man's blindness is a chance for him to do the works of light. He kneels, begins making the balm of healing, the good earth and his holy spit, and spreads it on the man's eyes.
If we can blame the victims for what has happened to them we need not be so bothered. A pact with the devil? Hundreds of years ago? Neither these poor unfortunates nor their parents sinned in such a way, or even if they did God is wise enough to see past such foolishness. The question is not why...the imperative is now: let us do the works of light while there is light.
God does not send earthquakes; but God's people send aid, as God sent aid to us in Jesus. In that way God is glorified in even horrible moments such as this.
Pray. Do not blame.