MAROONED somewhere in Russia, living in secret and with the time on his year-long asylum running down, Edward Snowden has at least one thing to be happy about. He had always said he hoped his leaks would spark a debate. He has certainly got his wish. The electronic spying of the National Security Agency and its foreign collaborators has been leading the news for months.

The spy agency has powerful defenders, but increasingly it has powerful opponents, too, with everyone from senators to retired generals to the President himself arguing (or at least paying lip-service to the idea) that things have to change. It makes an instructive contrast from the early days, when Mr Snowden was dismissed as an embittered narcissist and a loser. The latest recruits to Mr Snowden's banner are the bosses of eight big computing firms, who sent an open letter to the government yesterday demanding that the spies have their wings clipped.

As my colleague points out, the letter is a good sign that American technology businesses are worried. The idea that American web services are not as trustworthy as you might think is potentially very damaging. It's impossible to know how damaging, exactly (although that doesn't stop people coming up with improbably specific numbers such as $35 billion by 2016). But, besides the reputations of individual firms, it is worth remembering that America's computing industry as a whole benefits enormously from being overseen by a democratic government which embeds freedom of speech in its constitution. Before Snowden, there was a lot of distrust of firms like Huawei. But no-one worried about Cisco. That is no longer true.

Interestingly, though, Cisco is not one of the signatories to the letter. In fact, plenty of big tech companies are missing. The fact that only eight companies could be persuaded to sign may be revealing in itself. All of the firms that did sign are software houses. Hardware companies (like Cisco) are entirely absent, even though one of Mr Snowdens' many revelations is that the spooks have been spending plenty of money and sweat trying to subvert their products. Big telecommunications firms like Level 3 and AT&T, whose fibre-optic cables the spies have been tapping, have not said anything either.

Why not? One possibility is that consumer-facing companies have much more to lose from the bad PR that comes from cooperating with the spooks than do the firms that provide the (mostly invisible) infrastructure on which the internet runs. (On the other hand, Amazon, which is very definitely a consumer-facing company, is another notable non-signatory.) A related possibility is that the big infrastructure companies have no real competitors, at least as far as consumers go: if you dislike the idea that AT&T or Level 3 work with the NSA, there is very little you can actually do about it, and so the firms have no reason to risk upsetting governments by complaining.

One also gets the feeling that the companies that did sign may be playing with fire. Invoking grand principles about people's inalienable right to privacy is a commercially risky strategy. The entire business model of firms like Google, Facebook and Twitter relies on harvesting intimate information provided by their users and then selling that data on to advertisers. Bruce Schneier has pointed out that the NSA's global dragnet is really a public-private creation. It was private firms that persuaded people to give up lists of their friends, their most sensitive personal communications, and to constantly broadcast their location in real-time. If you had told even the nosiest spook in 1983 that, within 30 years, much of the populace would be carrying around a tracking device that kept a permanent record of everywhere they had ever visited, he'd have thought you mad. To a large extent, the spies simply helped themselves to data that were already there. If the companies are too vigorous in their defence of personal privacy, it might inspire their user base to demand changes in the way their personal data are handled.

A final thought is one that I've mentioned before. The letter demands reform of the NSA, more oversight and more transparency; in other words, a big, top-down, legislative and cultural change. They may not get it, and even if they do, it will take quite a while. But the big internet firms can act unilaterally as well. Mr Snowden himself has said that "encryption works. Properly implemented strong crypto systems are one of the few things that you can rely on". Several companies have been taking advantage of that, announcing plans to scramble traffic in order to make life harder for eavesdroppers.

One advantage of that strategy is that it addresses a valid point that the NSA's defenders have been making: it's not just the West that listens in. There are plenty of other spy agencies in the world; some serve some fairly unpleasant governments. Even if the NSA is reined in, that isn't going to stop the Chinese government's secret police, say. Strong encryption, on the other hand, works against everyone.

Assuming, that is, that your customers trust you to implement it properly. Another, less remarked-on side-effect of Mr Snowden's revelations is that they have made it very difficult to know who to really trust. A year ago talk of giant, globe-spanning electronic surveillance systems would have sounded like shooting-range conversation amongst the black helicopter crowd. But the revelation that this particular conspiracy is, in fact, real has made people jittery. A recent post on TechCrunch pointed out that Microsoft's recent pledge to encrypt its services to thwart eavesdroppers contained a curious exception: Skype, the firm's popular and supposedly secure voice and video chat service. Microsoft says that Skype was left out simply because the firm didn't feel the need to exhaustively list every single service that would now be encrypted. A year ago that would have been reassuring. These days, perhaps not everyone will believe them.