There's an idea at the core of Jeremy's thoughts here which struck a never, one that is best summed up in two quotes, one from Jeremy and another he quotes from Jamais Cascio (here given with Jamais first, Jeremy second):

When something is brittle, it’s susceptible to sudden and catastrophic failure.

It’s not that brittle sites don’t work. They work just fine …until they don’t.

I agree that brittleness is often a result of how things look fine. Jeremy makes the point that we have a "natural bias towards what's visible" and that's true. When the breaking points of our sites are invisible – because we're using fast connections, we're close to the server, we're operating on a desktop with a good screen, we're using a mouse to navigate – the site looks robust. But robust is not the same as "hard to break". It looks strong, but it may just be brittle.