Why do worldly disasters still happen?

This is a qn answered by Pastor before during the Tsunami period. But another great disaster has happened again - the earthquake in Haiti. And with that came another wave of prodding questions - Why do natural disasters happen? And why does God allow them to happen? And taking it one step further - What happens when there's a believer living in the area believing in protection. Does God allow him/her to be harmed? Perhaps God may move the believer out of danger but what if the believer prays for protection over the whole country/area. Is not God big enough to accomodate that prayer?