Depends at what cost - if it means a reduction in freedoms which are at the core of Western democracies, if it encourages terrorists to carry out even more attacks, then no - it's not worth it.

The 'if it saves just one life' argument is used under all sorts of circumstances and yet is in many cases judged not worth the cost.  Fitting limiters on all vehicles to a maximum of 25mph would save lives but most would agree that doing so is not worth the cost for all sorts of reasons.