Ellen Nakashima for the Washington Post:

“An analysis of 225 terrorism cases inside the United States since the Sept. 11, 2001, attacks has concluded that the bulk collection of phone records by the National Security Agency “has had no discernible impact on preventing acts of terrorism.”

In the majority of cases, traditional law enforcement and investigative methods provided the tip or evidence to initiate the case, according to the study by the New America Foundation, a Washington-based nonprofit group.

No idea how credible this Foundation is though.