However it's important to remember that one the intelligence is collected and shared it's then in the hands of men to ACT on it. The intellegence was there...men refused to act in the case of the Boston Bomber.
Regardless of how sophisticated our machinery is...it requires human action..and humans will never be perfect this side of heaven.
Which is exactly why we have a 4th Amendment, heck, why we have an entire Constitution meant to constrain the powers of the federal government. Tens of millions were killed by their own governments last century. I'll chance an occasional missed terrorist attack over the clear danger our out-of-control government is beginning to represent.