That's a really great way to put it, captures the powerful intuitions on one side of the issue here.
On the other side, well, we've been down some similar roads before. It's easier to see in the exploding Pintos and combustible Volkswagens. It's a common theme throughout the macabre history of modern (US) product liability: How much responsibility does a company have for accidents that it could prevent, but at some obnoxious cost? [1][2]
At one point, some judges had a simple rule. Just run the numbers. If you can prevent more harm than it costs you to fix, you better fix it. If not, eh, good call, save your money. Don't spend millions to prevent one stubbed toe every ten years, that'd be a waste.
Seems sensible. Until it gets applied to harder cases.
Sure, they did the tests. They knew their Pinto would burn a few hundred people to death each year. But they ran the numbers. They used the right value for life, were careful in their choice of actuarial tables, and used conservative costs for the upgrades. It was just too expensive. I mean, they'd have to be hit just right, perfect angle and velocity. Better to put the exploding fuel tanks on the road.
Maybe not better for Lilly Gray, trapped in a burning vehicle, skin sloughing off, pain so extreme her heart eventually quit.
But you know. Better for society.
So the resulting case[1] tackles that inevitable question: is this really enough? Ford clearly forecasted the future. They saw Lilly Gray's charred corpse in the crystal ball, or someone like her. They didn't do anything to stop it. They followed the law instead, because it was cheaper or more expedient. Are we really going to let that slide?
Ok, that's verging towards polemic. Let's pause. Let's swing back the other way: How many accidents is a company expected to prevent? Should every car be wrapped in thousands of dollars of bubble wrap, or whatever the steel equivalent is? Should every car come equipped with roll cage and handy fire extinguisher, prepped for battle on the NASCAR track? Should these hefty tanks then run on nearly inert fuel to prevent engine fires completely, capping their range at a few paltry miles?
Clearly there are extremes.
So let's drop the absurd extremes and go back to the common, the real issue. Back to Google's problem: avoiding the simple rear end collision.
Given enough data, enough predictability, you're going to see some subtle shifts in the notion of blame.
Especially when you start looking at the issue of "fault."
In most (all?) US states, juries divine a "percentage at fault" for both parties before proceeding to divvy up damages.
You're going to get at least a few juries claiming that, sure, the rear ender was 99% at fault, everyone can see that. But that savvy defense lawyer has a point: Google was at least a teensy weensy bit at fault, just barely. With all their data and slick technology, surely they could have done something. Surely they're responsible for not improving their algorithm ever so slightly to handle this particular case. Let's call it 1%. No more, certainly, but no less.
Conveniently enough - it's enough to get the case dismissed without any damages whatsoever. At least in a few US states.[3]
N.B. - I sharked you a bit here and I apologize. In my original post, I said Google wasn't at fault, "legally speaking," but "legally speaking," nothing's really ever that simple.
[1] http://users.wfu.edu/palmitar/Law&Valuation/Papers/1999/Legg...
[2] http://caselaw.findlaw.com/us-supreme-court/444/286.html - ok, doesn't really get all the way to this point, but the facts are startling, and prime the discussion. It's a harrowing story and explains a lot about how product liability works and why it exists.
[3] https://en.wikipedia.org/wiki/Contributory_negligence