Surveillance cameras didn't deter the terrorist attacks in London. They didn't stop the courthouse killing spree in Atlanta. But they're prone to abuse. And at the end of they day they don't reduce crime.
In New York, the authorities are doing random searches to look for explosives.
Yesterday, the London transport system was flooded with police, many of them armed.
All these policing measures are controversial - how to evaluate them?
The exceptional density of CCTV in Britain, and especially London, is a legacy of previous terrorist campaigns. I am surprised to see Schneier dismiss them so totally, as they are a cheap way of getting substantial benefit. Cheap both in money and in "social cost" - when you are out in public you can be seen, but with cameras you can be seen by people who weren't actually there at the time. You can disguise or hide yourself, at the price of looking a bit suspicious. The images (unlike, say, number plate recognition cameras on motorways) can't be used for broad sweeps to track people over months or check everyone for a particular behaviour. (note also many of them are in private hands - the police have to ask for them, and they need support from the public to get them). I'm absolutely opposed to compulsory ID, large-scale telecoms interception, etc., but not CCTV.
From where I sit, it looks like CCTV has been the key tool in breaking up the terrorist organisation behind the London bombings; tracing the 7th July team back to Luton and Leeds, identifying the 21st July team, and following both leads back to contacts and resources.
To be fair to Schneier, all these developments happened after he made the quotes above, but they are consistent with previous terrorist campaigns. Possibly we in Britain see counter-terrorism differently -- Schneier, like Arnold Kling, is thinking in terms of preventing a one-off attack like 9/11 (which is almost impossible), while we naturally think in terms of winning an extended campaign, in which we take hits but use intelligence gathered to disrupt the enemy organisation. Even a suicide bomber, who is very hard to deter and who can't be captured afterwards, is part of an organisation - large or small - which is more vulnerable if he is identified and traced.
Random bag-searches, on the other hand, score very badly on price-performance. The expense and social cost of searching commuters' bags are very high, and the likelihood of them having any effect at all is quite low.
The large police presence yesterday was expensive (I would guess it cost on the order of a million pounds), and slightly unnerving.
Both of the last two are not cost-effective over a longer period, but each might make sense as a one-off or very occasional measure when the threat is judged to be high. I don't know whether that is the plan in NY, but it probably was the plan yesterday; if two of the 21st July bombers were arrested today, then yesterday was the day they were most dangerous. It's easy to imagine a suicide bomber succeeding in a mission under the noses of all those police, but there's a distinct chance that they would have been able to interfere with the mission. Estimate say 2% chance of an attack on that day, 20% chance of foiling it, a million pounds is fairly reasonable.
Ian Blair - disagreeing with me among others - says the 21st July team were not the B-team or amateurs. This is a relative question, and I would not expect or wish those with the job of catching them to be as blase about them as I am, but I stick to my guns:
Any fool can kill people; the chief attribute of these guys is not skill but bloodthirstiness - but even killing a few hundred people a year would only really affect our way of life if we let it.
This lot are much less sophisticated and professional than the IRA, and most importantly, don't have the community support the IRA had (how may IRA bombers were ever grassed up by their mothers?)
Sir Ian needs to take this as seriously as a football manager facing a lower-league team in a cup game, but for the rest of us we ought to be confident that we can beat these scum, without losing our sense of perspective.