If you're going to ignore chilling effects, then by that reasoning the NSA surveillance is totally harmless.
That's a ridiculous argument. The Beltway sniper killed 10 people in 2002, a fraction of the number who died in car accidents that year. But tens of thousands of people had their lives disrupted as they ducked down while filling up at gas stations.
Car crashes in 2002 were in the range of 30,000 deaths. Which is orders of magnitude higher than the sniper.
So in my opinion we shouldn't waste money on NSA wiretapping that doesn't stop terrorism (because if it did it would have stopped the Boston Bombing) and instead invest that time and money into transportation infrastructure.
By doing that we would save more lives, improve our economy and most importantly still have constitutional freedoms.
More toddlers with guns have killed Americans this year than terrorist have.
If we are trying to save lives, worrying about terrorism is a waste of money.