Investigative journalists rely on information sources to write interesting stories. Their work is a significant contributor to democracy and free speech in my opinion. Articles that expose wrongdoings within the private and public sector function as a social control when other channels fail to address an issue.
However, certain governments are not that keen on whistleblowers. Many of them choose to track them down and to prosecute them. As mass-surveillance and metadata retention programs are recording almost every aspect our digital life, it gets more and more challenging for the information sources to hide their real identities. The damaging impact on our society is that investigative articles could eventually stop being written as whistleblowers will be afraid to speak out.
The situation is not hopeless, though. Journalists can still do certain precautions to protect the identity of their information sources. A sensible combination of cryptography, privacy tools and OPSEC practices could help to keep those stories coming.