while i'm not so sure about benny hinn, i wouldn't be so quick to judge such an action by itself.
a pastor i respect greatly once told me a story about a time he was asked to pray for someone with kidney stones. they were painful, but not real bad yet... they had an appointment to disintegrate them with ultrasound about a week later. but still wanted to let God heal them.
when he went to pray, he felt God leading him to pray, not that the stones would dissipate, but that they would harden and dry up! really strange, and i'm sure he got weird looks from the person as well. sure enough, they did harden and dried up, and this meant that instead of using the ultrasound non-invasive technique, they had to actually open them up and do surgery. so far, sounds like a net loss.
but, after the surgery, the doctors told them how lucky they were... the person had an as-yet-undiagnosed blood disease that was nearly impossible to treat, and you can't do surgery on blood. but, when the stones hardened, all the infection got sucked into the stones, and they were totally clean of it afterwards.
god certainly works in mysterious ways sometimes, but he always knows what he is doing.
Each man's knowledge is genuine to the extent that it is confirmed by gentleness, humility, and love. - st. mark the ascetic.
You move from fear to religious devotion, from which springs spiritual knowledge; from this knowledge comes judgment, that is, discrimination; from discrimination comes the strength that leads to understanding; from thence you come to wisdom. - st. peter of damaskos