It represents a great improvement over other electronic navigation systems, and certainly over traditional methods. But you're right, it has its limitations and its vulnerabilities, and we certainly rely on it entirely too much. Other countries are quickly lofting their own satellite navigation systems into orbit, which makes you think other folks don't trust us to keep ours working in wartime, or that it could just underperform in peacetime.

It is a very complex technology based on an elaborate infrastructure and a huge government bureaucracy, and could be vulnerable to enemy action or exotic natural electric phenomena. What could possibly go wrong, eh?