You seem to be assuming several things: that this is peculiar to the iPad, that people who do understand the limitations also care, and that if they don't make fully informed choices about things they care about that it is someone's fault other than their own.
I don't think those are accurate assumptions.
But your last point is a good one. And I think it gets to the crux of a lot of the hysteria over this being a "closed system." A lot of consumers aren't very savvy when it comes to complicated electronics. Maybe that's their fault? I don't know. But something in me says it's partially Apple's responsibility to educate people about the devices they sell through proper marketing.
If Apple markets this ethically they won't mislead people into thinking this is a general-purpose computer. Because if people perceive this as a general-purpose computer, they will be sorely disappointed in a lot of ways when they get it home.
So It doesn't have to be entirely the manufacturer's fault if I make an uninformed choice, but I'd argue that it is partially the manufacturer's responsibility to educate me.
It is, but there are practical limits to that. We don't usually expect companies to highlight things about their products that some people might not like, we just expect them to not lie. Obviously they omit much, but omissions aren't inherently nefarious or misleading (I know you're not saying that), so we're talking about something(s) more specific than that. What should Apple be expected to make clear about their products that they aren't currently?
If Apple markets this ethically they won't mislead people into thinking this is a general-purpose computer.
Isn't it though? In the sense of 'tasks you can perform' or 'purposes you can use it for', it seems quite general. It has limitations in terms of what is available from the store, but how would you convey those to limitations to someone as being distinct from obvious limitations like how the lack of a camera prevents you from taking pictures with it?
I'm not sure if that's a clear question, but I ask because it seems to me that people with a less detailed understanding about how these things work tend to view software limitations as being just as real as hardware limitations, and that whether it allows them to accomplish the tasks they want to perform or not is vastly more meaningful to them than their control over how it does so. I just don't get the sense that people will be disappointed.