The NSA is claiming that the data that they grabbed in essentially warrant-less Hoovering up of telephone and Internet metadata has helped in certain investigations.
I have no doubt that is probably true.
But that is not the right way to frame the problem. The real issue is: Did being able to data mine metadata for all Americans help solve the case better and faster than had they been required to seek specific probable cause warrants for data from specific people?
To make clear the distinction, let's suppose I were trying to justify stealing a copy of every book in Barnes & Noble. I might be able to accurately say that those books helped me writing a good Napoleon paper for school. But could I have achieved the same goal - writing a paper on Napoleon - by purchasing individual books as needed via legal shopping processes? The answer is probably "yes." Having all the books pre-stolen only contributed in that it saved me the hassle of going down to the store and finding a specific book I needed.
In the same way, I suspect that having this data base merely saved FBI and others the hassle of filling out some paperwork in each case. I am not sure incremental success rates in a few cases is enough justification to rip up the Constitution, but I am sure that laziness is not.