* Germany stung by reports U.S. tapped Merkel's phone
* Some wonder if German chancellor is being naive
* Merkel had to evade East German spies in her youth
BERLIN, Oct 29 (Reuters) - When Angela Merkel was growing up in communist East Germany, she recalls her parents getting nervous whenever she talked for too long on the phone. "Hang up! The Stasi is listening and it's all being recorded," warned her mother, according to one biography.
But somewhere along the line between her childhood behind the Iron Curtain and becoming chancellor of a united Germany, Merkel apparently lost her fear of eavesdropping.
She called Barack Obama last week to demand clarification of reports that the U.S. National Security Agency had monitored her mobile phone. But the protests ring hollow to those who have warned about omniscient U.S. eavesdropping.
Critics say Merkel is either naive or feigning surprise for her domestic audience.
"Frau Merkel has been listened to since she was a teenager," said Frederick Forsyth, the thriller writer and former Reuters correspondent in East Berlin. "The only thing that amazes me about the furore is that it amazes people.
"Anyone who's been aware of what's been going on the last 30 years would presume all electronic communications are being listened to by someone," he told Reuters.
Before the Berlin Wall came down in 1989, East Germany's pervasive Stasi secret police had 2,000 spies and collaborators in West Berlin and West Germany - including a close aide to then chancellor Willy Brandt. It also ran a massive phone-tapping operation to spy on East Germans.
As a young woman in East Germany during the 1970s, Merkel, now 59, was herself approached by a Stasi agent, who tried to recruit her when she was applying for a university job. She turned him down, saying it was not something for her, she later told German television.
The skills of the Stasi's vast network of agents have not gone to waste in Merkel's Germany. Former Stasi cryptographers are now working with the German government, Der Spiegel magazine reported last month.
"SPYING AMONG FRIENDS"
After the eavesdropping scandal broke, Germany summoned the American ambassador for the first time in living memory, in the most serious breach between the two allies in a decade. "Spying among friends is not at all acceptable," said Merkel.
The public outcry has united Germans behind Merkel even though her position may be more of a domestic show than genuine outrage, in particular as she announced her call to Obama just as Spiegel was about to break the story.
In August, during the election campaign, Merkel and her ministers had first played down what they knew of the NSA's PRISM programme after reports suggested U.S. spies tapped half a billion phone calls, emails and text messages in Germany in a typical month, and also bugged German offices and officials.
"Merkel is pretending to be surprised," said Christian Lammert, a political scientist at Berlin's Free University. "Privacy is a huge issue in Germany and she's got to do this otherwise she'd have a credibility problem."
Michael Desch, a University of Notre Dame expert on international security, suggested that Merkel, who often uses an unsecured cell phone that security experts warned could be tapped even by hobby hackers, was being disingenuous.
"Revelations that the United States spies not only on its enemies but also close allies such as ... Germany demonstrate the old truism that great powers have no permanent allies, just permanent interests," said Desch.
Some senior German officials take it for granted their calls and emails are monitored. "When you're a member of government, you have to assume it's happening - from all sides," outgoing Vice Chancellor Philipp Roesler told Cicero magazine.
For columnist Hajo Schumacher in the Berliner Morgenpost, "the only problem is that the Americans got caught".
Forsyth, whose best-selling novels include "The Day of the Jackal" and "The Odessa File", said the German intelligence agency, the BND, invests heavily in eavesdropping.
"What the hell does she think all those costs are for?" said Forsyth, who covered the Cold War from East Berlin in 1963-64. "Have they no idea what's going on in this world?"
Some Germans view the U.S. eavesdropping of Merkel as a betrayal by the country that did most to defend democratic West Germany from Soviet-backed communist during the Cold War. The issue has dominated German media for the last week.
German authorities have sent helicopters on low-altitude flights to inspect the roofs of the U.S. embassy in Berlin - about 800 meters from Merkel's office - and a U.S. consulate in Frankfurt, German media reported.
Yet the shock and outrage are remarkable considering the history of Berlin, which was split by the Wall until 1989 and was a hotbed of espionage by East and West, where spy exchanges took place on Glienicke Bridge. The United States used West Berlin as a listening post for Eastern Europe.
In August, Merkel said the government had asked internet providers if they had any indications Germans were being spied on. "They all denied it," the chancellor said, adding that she was certain that she herself was not being monitored.
German officials say U.S. intelligence has helped foil half a dozen terrorist plots here in the last decade while Forsyth said Washington might think it has cause to monitor a country where the Sept. 11, 2001 attacks were planned.
"If you're going to use an unsecured cell phone, you're going to be listened to," said Forsyth, who does not use a computer or a cell phone. "The idea that listening to one's ally is something new is complete nonsense."