It's natural for humans to react to natural disaster and general misfortune with disgust. We think about natural disasters that devastate and feel truly sorry for victims.
Many theists believe that an all-powerful, all-loving, and all-knowing god created the universe and everything that happens is part of some divine plan. If God is good and all that comes from him is good, why should theists balk at the results of said divine plan? Theists would, I venture, ignore the implications of the naturalistic fallacy (that which is natural is good) because they believe that God is, by definition, good.
Christian friends of mine on Facebook are saying, "The residents of Japan are in my prayers." I understand, as I previously stated, why someone would be downtrodden when hearing about the events unfolding in Japan, but this sentiment doesn't seem at all consistent with a theistic worldview. I firmly believe that belief in an omni-god is irrational on the grounds of natural evil as I previously discussed, so the theist is already at a loss for consistency, but praying for the victims and being upset at the disaster seems to betray a Christian worldview and further demonstrate that the belief is irrational.
If everything happens according to God's will, it seems foolish to pray for the people who are impacted by God's plan because, of course, the plan surely won't be altered because some follower wills it to be. Humans, under the Christian worldview, are utterly hopeless to determine what God does if it is the case that everything happens according to God's will. He already put a plan in action, one would assume, and since a true belief was held when God made the plan (he is all-knowing), this belief can't be falsified because then God would have held a false belief (and he can't because he's all-perfect).
If God is all good and everything follows from God, you have to accept the reality that the conditions for life set up by an omni-god are far less than desirable and do not seem that they flow from the creation/plan of an omni-god. How can the theist deal with this reality and still profess that God exists and is all-good, all-loving, etc?
Praying for disaster victims is silly. If a god exists and has a plan, nothing you can will can possibly change such a plan. I suppose you can hope that people will survive, but many have already died through no fault of their own...and are you going to seriously think that part of God's plan is killing hundreds of people via a natural disaster? Certainly not.
Praying for disaster victims shows a basic human emotion that betrays and transcends Christianity. You're acknowledging that you are concerned with the fate of troubled people and the outcome of a natural disaster instead of taking a line from the Westboro Baptist Church and praising God for his earthquakes.
Regardless of whether or not God exists, prayer does nothing to effect the outcomes of earthly matters. Scientific studies have not supported the hypothesis that prayer has a significant effect [statistically significant and demonstrable] on improving the health of people, so why bother?
How, as a theist, can you possibly hold a belief in an omni-god when you see egregious non-discriminate killing via natural disasters?
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In addition to the contradictions to belief, I care more about this topic for practical reasons. People who pray think that they are doing something to help and can easily forgo actually doing something to help a situation. You've certainly heard of children dying because their parents prayed for recovery of simple medical maladies instead of giving them proper medical care.