Whistle-blowing website Wikileaks is once again at the centre of attention. Sweden has cancelled an arrest warrant against its founder Julian Assange on accusations of rape and molestation. But the damage may have already been done. When reporters from The Washington Post uncovered the Watergate scandal in the early seventies they were hailed as heroes. But after publishing more than 90,000 leaked documents on the war in Afghanistan, the work of Wikileaks editors has been denounced as "a criminal act". So has the impact of whistle blowers been reduced? Are they more vulnerable now? And are they the future of investigative journalism?