Who gets to decide if there is "no reasonable need"? Apple clearly believes (just like the microwave manufacturer) that there is "no reasonable need" to extend the iphones software.
The iPhone is pretty much marketed and sold as a multi-purpose computing device. There is a huge market for installing software on it, there is a development environment etc. People know this when they buy it. It is very obviously a computer-phone.
When you buy a microwave, you are buying it to heat food. You are not expecting to be able to browse the web on it or play games. If you are, then you need your head examined or to invent this new product (if you are right that it's a reasonable/desirable expectation, there should be a market for it). I think the distinction is actually very very clear, continuum or not.
Once the microwave starts allowing for remote control and twittering its status, the line does become more blurred ;)
So, iPod classic is OK but iPod touch is not? What about a TV? A TV that can play youtube viedos? A car? The kindle? The drobo? Are they all multi-purpose computing devices? The distinction is actually not as very very clear as you think.
Anywhere minor modifications to the firmware could cause serious injury, it makes sense to restrict access to the firmware, because the firmware is a very small part of a hardware system that has been well-tested for safety. This makes the car and the microwave off limits.
iPod classic, it's not going to hurt anyone if you screw with the firmware, you should be free to tinker to your heart's content. There are also enough obvious deficiencies (lack of support for a variety of codecs) which can be improved.
Clearly the success of the app store shows that there's a desire to extend the functionality of the phone. Apple just doesn't believe that there's a reasonable need to do it beyond a certain point or to do it without their permission.
However, no one is clamoring to write apps for a microwave. A microwave really just has one function and as long as it does that one thing then it doesn't really matter how the software works.
What if I want to change what the buttons do? On my microwave, you have to type in the power setting before the time, what if I always want to default to 100% power unless I hit a specific button first? What if I want to hook a smoke detector up to the microwave so it will automatically shut off if its burning something?
I can actually see the point of the microwave running software that you can't mess around with, it wouldn't be too hard to bypass the safety like that and someone might end up getting hurt. That said, there are plenty of other ways in which you can hurt someone using a microwave that do not involve the software, taping out the interlocks, rewiring the thing and using it as a blunt weapon are a few.
Tinkering with the software on your phone has much less potential to do so, for me it's simple if it has software in it and you bought it then you should be able to tinker with it.
