Oslo - Praised to the skies and bearing great hopes, they went on to disappoint the world. As the case of Myanmar's Aung San Suu Kyi shows, Nobel Peace Prize winners have not always lived up to expectations.The Norwegian Nobel committee's announcement every October is usually followed by some protest and occasionally a heated debate. Rare are the laureates who are unanimously embraced. Aung San Suu Kyi was one of those.Honoured in 1991 for her pro-democracy resistance to Myanmar's junta, the wispy "Lady of Rangoon" was long hailed as a saint. But now, as Myanmar's figurehead leader, she has been broadly criticised for failing to protect the Muslim Rohingya minority from what some world leaders are calling "ethnic cleansing"."I'm disappointed," said Geir Lundestad, the influential Nobel committee secretary from 1990 to 2014."Aung San Suu Kyi was an extremely popular and deserving laureate, heroic under the circumstances, but I can't condone her behaviour toward the Rohingyas," he told AFP.Suu Kyi's supporters and many observers say she lacks the authority to rein in the military, which ran the country for 50 years and only recently ceded limited powers to her civilian government.Nevertheless, almost 430 000 people have signed an online petition calling for her Nobel to be withdrawn, and several other well-respected Peace Prize laureates - Desmond Tutu, Malala and the Dalai Lama - have urged her to take action to end the violence."It's dramatic," admitted Nobel historian Asle Sveen. "For a person who fought so hard for democracy and was so popular for so long to find herself in such a situation, it's unusual."Unusual, but not completely unprecedented.While Suu Kyi may be in a league of her own, other Nobel stars have also seen their lustre fade over time.Flagrant faux pas For starters, there's former US president Barack Obama - "the most similar case", according to Sveen. His 2009 Peace Prize, awarded just nine months after he took office, was met by many with incredulity, but at the time, he was still at the peak of his popularity.Eight years later, there are still calls for his prize to be withdrawn, especially on social media, because of his failure to end the wars in Iraq and Afghanistan and his intensive use of drone strikes."It was impossible for anyone to meet those expectations. They were totally unrealistic," Lundestad said recently. "I don't think the committee expected Obama to totally revolutionise international politics: it's not about transforming everything, it's about making steps in the right direction."Other laureates have been accused of committing flagrant faux pas.Lech Walesa - the founder of the Soviet bloc's first independent trade union Solidarity and who won the 1983 Peace Prize - has repeatedly been accused of collaborating with Communist secret services.Rejecting the allegations in 2009, he threatened to leave Poland and return his awards.Long before him, Italian pacifist Ernesto Moneta was criticised for having supported his country's decision to go to war against the Ottoman Empire in 1911, four years after receiving his Nobel.Austria's Bertha von Suttner, the 1905 laureate and a close friend of Alfred Nobel's "proposed that Moneta lose his Nobel Peace Prize and his titles in the peace movement", recalls historian Ivar Libaek in the collective work "The Nobel Peace Prize: One Hundred Years for Peace".'No one's perfect' Twice during the post-war period, the choice of Nobel Peace Prize laureate has been so explosive that some committee members have resigned.One quit in 1994 to protest against the choice of Palestinian leader Yasser Arafat alongside Israelis Shimon Peres and Yitzhak Rabin, a year after the signing of the Oslo Accords. Two others stepped down in 1973 when US secretary of state Henry Kissinger and Vietnamese peace negotiator Le Duc Tho were honoured for reaching a ceasefire - albeit short-lived - in Vietnam.Each time, the debate has smouldered for years."He won the Nobel but he dishonoured it. Whether he returns it or not doesn't matter, it must burn his hand when he touches it," fumed former Nobel committee member Berge Furre in 2009 about Peres. The career politician, who was Israel's president at the time, had defended an Israeli attack on a Gaza school that left more than 40 people dead.While Le Duc Tho immediately declined his prize, Kissinger accepted his but chose not to go to Oslo to pick it up for fear of massive protests. In 1975, he even offered to hand it back.The committee refused. The Nobel Foundation's statutes do not allow for it. Neither do they allow for a prize to be withdrawn."None of the Nobel laureates is perfect," Lundestad said."Many of them probably feel an extra responsibility to act in an exemplary fashion, but once the prize has been awarded, the committee can't do anything anyway."This year's prize will be announced on October 6.