The thing is: How can they check or double check? It's a confidential memo from an anonymous user. If it was possible to check it, that wouldn't be a big news ;

The thing is: How can they check or double check? It's a confidential memo from an anonymous user. If it was possible to check it, that wouldn't be a big news ;-) And yes, I do agree that anonymous tips have no credibility. However, experience shows that some anonymous tips were true and, especially when it's the only information you have, might become relevent.