The NSA has the often thankless task of defending the United
States in a dangerous world. When it fails, and a terrorist succeeds in doing
harm to American interests, it is subjected to harsh criticism. When it
succeeds in averting terrorist attacks, it cannot advertise its achievements,
for fear of alerting its targets to its methods and insights. The result is
that the American public cannot know how good the NSA really is. All we hear
about is when it oversteps its bounds (as defined in retrospect) in its
defense of our freedoms.
When you are the world power and you are 50% of the world's military budget, I guess it is okay to be a little paranoid and want to watch your tail. I would much prefer the United States be a more peaceful nation than have to have programs like the NSA, but I suppose it is necessary.
The National Security Agency (known as the NSA) has gone way too far in its abuses of power in recent years. This has been made clear by the revelations of people like Edward Snowden, who leaked a vast trove of information about the real things that our government has been doing.
We have absolutely no evidence that there are any pros associated with the NSA. Documentation indicates that their efforts have done nothing to stop possible attacks. The cons however are affecting the country in a very negative way, from the common citizens trust of the government, to companies ability to function in the global economy.