I sympathize with those who are frustrated by the claim that we can't be sure that Osama bin Ladan is in hell. Hell certainly exists, people can certainly be damned, this man's sins were certainly damnable. How can we not be certain he is damned?
But let me ask it the other way: How can we be certain?
There are two ways to be certain, about anything: knowledge and faith. By faith, we are certain of the universal premise, "All who die in unrepentant moral sin are damned."
By knowledge we are certain of ... actually, we aren't certain of anything. We don't know the state of anyone's soul at death (even a canonization or a private revelation gives certainty only by faith).
We may have a pretty darn firm opinion of the particular proposition, "This man died in unrepentant mortal sin." But -- and this just adds to the frustration, especially for think-out-loud moderns -- we have been commanded by God to abandon opinions of that kind of particular proposition.
Rather than being frustrated by the commandment against judging even in the most obvious cases, rather than being frustrated even by those who go too far in saying, "If we can't be certain any one person is damned, we can be certain no one is," we might profitably meditate on the why of the commandment, on the meaning and effects of that epistemological gap, unbridgeable in this life however short it may appear, between the premises we accept by faith and the conclusion we all but can't help jump to.