Chancellor Angela Merkel, a paragon of self-control and a master of the well-balanced word, has hoisted the red flag. Psychologists would say she has exceeded her otherwise high tolerance for frustration.

Her choice of words was revealing: "Totally unacceptable" and "a grave breach of trust," among close friends, the chancellor said after learning that her mobile phone had been tapped by the US spy agency, NSA.

Volker Wagener is an editor at DW's Germany desk

Just a few months ago, the same Angela Merkel was surprisingly mild in her appraisal of the newest details concerning US surveillance practices. She issued only a few appeals directed to Washington for an explanation. The whole affair, initially unleashed by the spectacular revelations of Edward Snowden, a former US intelligence contractor, evaporated like dew in the heat of the daily political grind.

Overstepping a taboo

Now, however, the chancellor is outraged. One could insinuate that Merkel is applying a double standard: Here, the anonymous masses of ordinary German surveillance victims; there, her own cell phone - the official communications device of the Chancellor of the Federal Republic of Germany.

But that's not it. This is all about breaking a taboo. Merkel is the framer and shaper of German policy. To eavesdrop on her is a hostile act. Only, it is not an enemy resorting to the weapon of surveillance; it is a friend - an ally. That makes the entire issue especially delicate.

Espionage, perhaps the world's second-oldest trade, was an inherent part of the Cold War. And quite obviously, this craft, which thrives in the shadows, is flourishing. It is just that the source has changed.

Who needs enemies when you have friends like this? Nobody would bat an eyelash, if this were Moscow or Beijing thirsting for details of our economic or political agenda. We even quietly assume that they are doing so.

But Washington's behavior strikes at very personal, existential German sensitivities.

First of all, spying on German citizens is a blatant violation of the rule of law. In particular, since we Germans have a very high standard of civil rights and data protection, we are outraged at this arbitrary surveillance.

Secondly, Germany is one of America's closest allies, and we expect to be treated as such.

Thirdly, our sympathies for President Barack Obama in recent months have been thoroughly upset due to the NSA scandal. And now this: Mr. Obama, the nice man in the White House, is listening in on Merkel's cell phone conversations!

NSA has lost its senses

Among friends, such a violation of trust would either mean the end of the friendship - which would be political nonsense in this case - or a hefty political blowup. No one but a close friend has the right to broach difficult issues and, when necessary, provide touchy recommendations.

In this instance, that means giving the United States the advice that it needs to get a handle on the paranoia triggered by the terrorist attacks of September 11, 2001.

The most suitable solution would be a more transparent handling of friendly relations and a retraction of the tentacles of the NSA octopus. This agency has long surpassed the many absurdities practiced by the communist East German State Security apparatus until 1989. And that's saying something.