[ska]

> UK viva (oral) examination is far less of a foregone conclusion,

That matches my limited experience with UK, although I've seen north american ones without a foregone conclusion - seems really dependent on institution.

> The most common way to "fail" is to simply not submit the thesis.

I think that's true everywhere, lot's of people just don't complete. I've heard somewhere that the "ABD" (all but dissertation) rate in US is nearly 50% at 10 years, if you go across all disciplines.