The terrorist barge/scud scenerio is highly implausible. Satellite imaging would detect such an operation off shore. The various intel agencies monitor our coasts very closely. We may not be able to stop every crazy with a box cutter, bomb belt, or even a dirty bomb, but missle strikes are another thing.
Also, it's my understanding our coasts are constantly patrolled by defensive aircraft. The moment a short-range missle was launched, they would head to intercept with air to air missles which would be faster, providing they are within the required proximity to the scud. With our technology and defense capabilities, I just don't see that scenerio happening.
Besides, the whole paranoid scenario sounds very American, and certainly not Islamic. If they had a scud with a nuclear warhead, they'd aim it at New York, not at the stratosphere.
Oh I hope you're right. This article really frightens me.