Despite everything you've gleaned from spy novels and movies, the most important raw material for a successful intelligence service isn't information; it's judgment.  If you don't know what information is worth collecting, and if you cannot figure out what this information means soon enough and clearly enough for policymakers to use it -- you lose.

The latest case in point is the fuss over allegations in the German press that our country's intelligence service has been listening in to Angela Merkel's cell phone conversations.  From the moment these allegations began to surface, American commentators and television talking heads -- a few of whom have actually served in US intelligence, most of whom claim to be intelligence experts because they once, perhaps, were allowed to read a classified document -- have been pooh-poohing these allegations as much ado about nothing.  "Everyone does it," they pronounce, usually with a shrug and a wink.  "So what's the big fuss?"

Yes, it's true that from time to time allies do spy on one another.  France, for example, is infamous for running industrial espionage operations against America's leading high-tech companies.  (It doesn't seem to have done the French much good; their economy is a basket case.)  But just because our allies put more effort into spying on one another than spying on their real enemies, that doesn't mean we should too. 

In the real world of intelligence, it isn't possible to know everything about everything.  You can never have enough spies, enough satellites, or even enough bandwidth to monitor all humanity.  And even if you had an unlimited supply of spies, satellites and bandwidth, there aren't enough analysts in the world, let alone in Washington DC, to make sense of what's been collected.  If you try to know everything about everything, you wind up knowing nothing about anything.  An effective intelligence service must pick and choose its targets very -- very -- carefully.  And that's a matter of judgment.

What could we possibly hope to learn from Angela Merkel's cellphone conversations that's worth the risk of offending one of our country's most important allies?  Is she likely to be calling China's president to co-ordinate an invasion of Russia?  Is she on the phone with the head of Pakistan's army to secretly purchase one of that country's nuclear bombs for the Luftwaffe?  Are you kidding?

This is Angela Merkel, one of the world's most capable, serious, head-screwed-on-straight leaders.  There isn't a chance she would do something to start a world war or fracture the Western alliance.  It's more than likely the most interesting call we'd pick up from the German chancellor is a conversation with her husband saying she'll be home late for supper because a delegation of Greek bankers has unexpectedly arrived in Berlin to beg for yet another Euro loan.  And you don't need spies or wiretaps to have predicted this -- or to predict Merkel's response to their pleas.

Meanwhile, it seems that none of our country's senior intelligence officials thought it worth the time and effort to keep an eye on the Tsarnaev brothers in Boston before they exploded two bombs at the Boston Marathon -- even though both brothers were growing more radical by the week, had set up a terrorist-type website, and one of them had traveled to Dagestan, and after returning to the US was the subject of a tip-off from Russian intelligence.  And before that, our intelligence service completely missed all the warning signs flashing red from Major Nidal Hassan in Texas -- emails to and from al Qaeda operatives, overseas phone calls to known terrorists, personal outbursts that would have alerted your average high-school guidance counselor, even calling cards with Soldier-of-Allah imprinted after his name -- before the army psychiatrist killed 13 people and wounded 31 others at Fort Hood back in 2009.

No intelligence service can be perfect, and even the most brilliant, hard-working spy chiefs will suffer the occasional failure.  But as the Angela Merkel dust-up and the other failures make clear, the problem with American intelligence today isn't a shortage of resources needed to keep us safe, but a lack of judgment at the top.

Herbert E. Meyer served during the Reagan Administration as Special Assistant to the Director of Central Intelligence and Vice Chairman of the CIA's National Intelligence Council.  He is author of How to Analyze Information and The Cure for Poverty.