The fact that shoes are screened so closely here makes it next to impossible to use them on US flights. With the increased awareness it makes it less likely even at airports that don't use the same screening we do. That does not mean that there is no threat from it, seriously it takes 15 minutes to make a shoe bomb, it takes about 30 mins to make a pair of shoe bombs. You do not know what anyone is thinking unless they tell you (and even then it is a crap shoot), so to say that no one is trying to harm aviation by using shoe bombs is like rolling dice. This does not mean that I think there are legions of loonies with a pair sitting in the closet waiting for the day they cna use them, it simply means that this is a tool in the terror loony toolbox, and one that is fairly simple to use in the right circumstances.