hi d&o,
my point is that there are other means to catch terrorists than a gigantic database of all the world's data. so the gripe you describe does not become illegitimate in the event of a successful terrorist attack.
on the basis of an argument like this or j-t's, you might demand that everyone has a brain-reading chip implant if one were available.
because if you object, boy, you have no cause to gripe in the event of an attack because you said you don't want the op.
and j-t might say, everyone should have the implant because there's a risk of nuclear war if they don't.
you can use the extreme case to justify absolutely anything you wish.
but the tradition of liberty is that you get to investigate folks who have given grounds for suspicion. free folks get protected from that.