They claimed 52 or 53 at first, then lowered that number to 1.
Then to zero.
There is no evidence whatsoever that this dragnet surveillance has been useful in any way whatsoever in fighting terrorism.
I think you might also be seriously overestimating how many people actually want to attack the US. Terrorists have more or less become a boogeyman at this point, the chances of anyone in the west experiencing a terrorist attack are so ridiculously small.
I agree that more transparency is necessary, and that we must have an intelligent debate, leading, ultimately to dismantling the current mass-surveillance apparatus. But I disagree about the "undoubtedly" part. If you'd said "maybe" I might have agreed, but there's just no evidence. There is evidence of abuses, but no evidence of successes.
http://www.techdirt.com/articles/20140111/22360125843/nsa-go...
We don't know this. In any case, it's the wrong question as we have to ask ourselves what the cost really is. The gov could just implement a curfew, lock everyone up in their homes and then we'd all be 'safe'. This the fodder of many a scifi movie and it would certainly thwart the plans of 'bad guys'.