One of the few advantages of increasing entropy is I remember my first electronic calculator.
It weighed about 10 pounds, needed 120V, and could add, subtract, multiply, and divide. I think it could store one intermediate result. It cost the equivalent of about $150 in today's money. That was a breakthrough, because a year or so before the same machine cost about $500.
That was the end of my slide rule.
Within a year or two vastly smaller and simpler calculators cost about $50, and a few years after that they were essentially free. 
Now that was disruptive technology.
We've never seen anything like that in the world of the personal computer. Today's personal computers have been, in most meaningful ways, no more affordable than the Commodore 64 ($135 to produce in 1982).
Yes, after twenty-seven years we have at least a million times the storage and maybe five times the display capabilities at perhaps half the inflation adjusted retail price, but in terms of tasks like writing this post the cost/value equation of the personal computer is closer to the car than the calculator.
Why is that? I think it's partly because calculators, for most people, delivered 90% of their value very quickly. They were commoditized at birth. They were also born before intellectual property protection was fully developed -- in a sense they were "open source" from the start.
By contrast the early development of the personal computer clobbered products like the Data General Eagle, but then a relatively slow change in the value equation built the mother of all profit generating corporations -- Microsoft.
That's about to change. The Market can't solve problems like global climate change or the problem of the weak, but, eventually, when the driving pressures are big enough and with a bit of antitrust help, it will find an out.
The squeeze is coming now. It's coming from China and India, from Google's Chromestellation and Google's Android, from open source and the Target Trutech netbook. Oh, yeah, and from the Great Recession as well.
After all, what's a Netbook running Chrome and Linux but a calculator in drag? It's fundamentally complete. It's built entirely of plastic, silicon (sand) and a tiny amount of rare metals. All the technology development costs have been fully realized, and there's no vendor with true monopoly control. IP attacks won't work if China and India decide not to cooperate.
It's not just the Netbook. Android is open source as well. Stick an Android phone in a cradle with a 1024 display and a keyboard and you have a computing platform at hundred thousand times more powerful than the Commodore 64.
The squeeze has been coming, but in 2009 it's going to be obvious. The price of the personal computer has been doing a Wile E. Coyote -- running on air for 27 years.
This year, gravity is going to kick in. Within another two years we'll see very crappy netbook equivalents being sold for under $75. Maybe they'll be today's netbook, maybe they'll be an iTouch with external display and bluetooth keyboard, maybe they'll be subsidized Chromestellation machines -- but it's going to happen.
This isn't all bad for Intel. The computing must be done. They can sell cheap chips to the netbooks and the phones, and lots of chips to the Cloud.
It's tough for Apple, but they can sell a bundled set of fully integrated and relatively trouble free goods and services alongside new consumer goods. Still, it will hurt. They're going to have to introduce a sub-$500 general computing device in 2009. Remember that when Jobs disses a market he's usually lashing his engineers to come up with a solution.
Ahh, but then there's Microsoft and Dell.
For them, this is very bad.
It will be very interesting to see what they try to do about it.
 Today, because they're so exotic, engineering and finance calculators cost more than they cost in the pre-PC 1980s. Or, if you have an iPhone/iTouch, you can run a superb emulator for a pittance.
Update: I left something out of the equation.
Update 1/1/09: This post on Netbooks running Android must have been written at about the same time as my post.
Update 1/2/09: I previously praised a 2007 Dan's Data review of low cost Linux laptops and connected it to the Newton eMate. In a f/u comment on the eMate I note the missing element of the proto-Netbook world of the 1990s (1980s if you count Tandy's famous proto-laptop) -- cheap wireless LANs. I'm still thinking about the Comcast role -- Netbooks aren't necessarily cheaper than laptops if you account for network access costs. That's why the Obama administration's position on public wireless service is such a big deal. It's probably the most important technology policty they will make-- one way or the other.
Update 1/8/09: This Chinese pseudo-x86 "Godson" chip development project is more than slightly relevant.
Update 1/22/09: Microsoft agrees. They're not stupid.