They're zoomed because it's the only way to demonstrate the difference when the display you're looking at almost certainly has a lower PPI. It's no different from having to zoom in on a print sample to show how clear a printer's text is on a monitor.
> Clearly, higher resolutions up to some point are better for display purposes, but there's tradeoffs involved. I believe smaller pixels means less light gets through, it's more work for your processors which means less battery life, etc.
Which makes it all the more impressive that iPhone 4 has four times the contrast ratio and better battery life than previous iPhones, with the speed of an iPad, in a physically smaller space. Given that everything has been improved, it's clearly not much of a tradeoff.
FYI, iOS is perfectly capable of running applications designed for other resolutions. It's not for lack of 'flexibility' on the operating system's part that Apple chose not to utilize intermediate resolutions for its hardware.
It's also a little strange to see Android phones' variety of resolutions being described as some sort of path that Android has trailblazed. For one thing, the operating system has nothing to do with it, and for another, that sort of thing has been standard practice for a long time now, whether you're considering computers in general or even just mobile handsets.