One of my biggest fears for computing is that we'll be denied even our linear bounded automata. I fear that instead of the general-purpose computing that Doctorow eloquently describes, we'll be forced to use what I call DRM machines instead.
A DRM machine isn't a generalised computer with Digital Rights Management code on it, as this poses less threat: the machine code can be inspected, and somebody can break the shackles. Somebody will always be able to circumvent such DRM eventually, no matter how much complexity is woven into it. Security by obscurity is expensive and fragile, and can't ultimately stand up to scrutiny.
No, the ingredients for a DRM machine are secure boot, and cloud computing. Using secure boot, you can make a machine that can only boot into a single guaranteed configuration. This could even be burned into the hardware, so that the secure boot mechanism itself is unconfigurable. Then such a machine can be made to securely boot into a system that phones home to some panopticon master.
Secure boot by itself is not evil. It's morally neutral. You can have a secure boot machine that securely boots to Debian GNU/Hurd. If a hardware boot was used, then you wouldn't be able to do certain things with the basic system, but Debian GNU/Hurd is a free OS, so you'd still be able to extend it, run an emulator on it, and so on.
A DRM machine, on the other hand, could be set up to check every action that is taken by the user. Every action could be delegated to a central authority point, that would check the "legality" of the action, according to some private specification of rules.
But why would people use such machines? People won't walk into a prison, will they? Sadly, it seems that time and time again, they will. There are already systems that are quite close to this scenario, in the games console world. There will be similar incentives, or pathological ideologies; there will, either way, be psychological tricks that coerce people into these systems. It will happen.
The best thing to do with a DRM machine is to smash it to thousands of tiny, unusable pieces. It should not be possible to recover a working system from a smashed DRM machine, otherwise it has not been smashed to its full potential. There may be laws enacted against smashing a DRM machine, with parallels drawn to how it's illegal to deface a banknote. The DRM machines may be considered a true servant of the state, and be given legal protections greater than those of humans. As true servants of our oppressors, they would need to be smashed.
General purpose computers would be the new samizdat. But they would be extreme contraband, far more feared than the printed word. They are the executable word. Possession of a general purpose computer would invoke instant severe repurcussions. Knowledge of how to create, maintain, and use general purpose computers would be amongst the things most strictly and stringently forbidden in any use of the DRM machine. The DRM machine would ultimately evolve to resemble a general purpose computer in as few characteristics as possible.
The most disturbing aspect for present computing is that the DRM machine can be created using off-the-shelf components which are, by themselves, morally and relatively ideologically neutral. Secure boot and cloud computing are not facing the ire of those who, some decades ago, were involved in the CND. But we could also use off-the-shelf components to create a truly secure, distributed network, impervious to eavesdropping and tampering. Just as a DRM machine is within our reach today, so is a brighter future. Those who have it in their power should make use of the available components.