I would apply the same to any "anti-terror" legislation.

The "effective cost" of any given threat is the potential cost when the threat becomes reality multiplied by the chance of it happening.

The potential cost of being a terror victim is high. You could be killed or seriously injured. We can give it a score of 1 (on the scale from 0 to 1). But the chance of that happening is quite low, in parts per million. Let's be generous and give it 1 in 100,000, i.e. 0.00001. Multiply the two and you get 0.00001.

The potential cost of the impact of any "anti-terror" legislation (say, the "Patriot Act") is hard to quantify as it depends greatly on everyone's personal circumstances. If you run Wikileaks or are a member of Greenpeace then presumably the cost is higher than if you work as a lollipop lady. But everyone is impacted to some extent and we can assume an average score. Let's say one ten-thousandth of the cost of being killed, i.e. 0.0001. But the chance of that happening is a certainty, i.e. 1. Multiply the two and you get 0.0001, which is ten times higher than the "effective cost" of being a terror victim.

These figures are of course hugely inaccurate and, in any case, assume only averages. The chance of being caught up in a terror attack is much greater to for example airport security staff or even frequent travellers. But I hope you get the idea.

So what can the government do to push through any personal freedom restricting legislation? Quite a lot, it turns out. They can hugely exaggerate the danger of being a terror victim. Easy to do, just make sure any incident is reported extensively. Media are willing, albeit usually unwitting collaborators in that effort ("bad news sell"). What else? They can play down both the potential cost of surveillance ("if you have nothing to hide, you have nothing to fear") and the chance of it happening ("it is targeting the bad guys, not you"). It is up to us to see through that BS.