I don't think that boats and cars/airport vehicles are actually destroyed when you blow them up (though please correct me if I'm wrong, and I'll leave and blow up some fuel trucks  ;)). If I'm correct, I think that the next update should allow you to explode ALL AI traffic and, as somebody said above, buildings (or at least have the missiles stop when they hit the buildings, weapon is very realistic and it's kind of disappointing to see my Hydras fly through walls without exploding). Cheers!