I wasn't trying to imply the insurance company wouldn't cover. What one would have to be insured for is negligence due to the modified vehicle. Possibly through an umbrella type policy. Taking the concept to an extreme, would you agree that just setting the jack on the hood was negligent when it became a projectile in an accident? I feel pretty sure after being on all sides in accident cases (including as a jury foreman) that a lawyer would argue for a large settlement arguing that an insecurely and/or improperly mounted object was negligent and increased the damage, caused death, etc. A jury could easily set an award that exceeded the limits of many policies. Example: Just today a local lawyer had a TV ad on in which he got $5,000,000 for a guy injured in an accident. What happened I haven't a clue, but I know $5mil is over my liability limits - would they come for my house, my 401K, etc.?
Negligence is what insurance is for. We're negligent when we speed, negligent when we don't look before changing lanes, negligent when we don't load our trailer properly... all those things are covered by our insurance policy. The insurance company gives us a contract that indemnifies us for our negligence, as long as it is
reasonable negligence (what a reasonable person would do). The umbrella policy only covers liability that exceeds the policy limits (auto pays first and then umbrella covers over the auto limits). But I don't believe it expands coverage scope beyond what the base policy does. For example, my home liability excludes firearms liability for intentional acts outside the home. My umbrella won't cover that if my home excludes it.
In your case of setting a jack on a hood and driving off that would be negligence but it also would be a covered at-fault claim should it cause damage. I would be money that leaving things on top of vehicles is something that reasonable people do and would be covered.. Only if it could be proven that you left it on your hood with the intent of causing damage would you be at risk of having the claim denied. Real world case: we had an unsecured load get blown off the top of a lift gate truck last month. Our driver was negligent in not securing his load. But it was a covered loss to the car behind him which took the box head on.
That you're at fault and that the coverage is voided are two different things. My big gripe is that it's not completely transparent to the consumer as to what conditions will void their coverage. Progressive, as an example, won't cover lifts over a certain height (at least that was the case when I had them several years back in Oregon, hence my switch to SF). This isn't stated anywhere when you sign up. It's only when you start asking questions do they tell you this. And the sales guy on the phone won't know either. You have to ask for an underwriter to make a judgement.
As far a the claim size, $5M is extraordinary. There was probably a story behind it. I keep $2M on top of a $500k CSL policy and sleep well with that.
At the end of the day, though, it's also about doing the right thing and being smart. I think all of us would rather avoid a big claim then be insured against one. Is putting a highlift on the front bumper the right thing? I'm not convinced it either is or isn't. Hence, the original question as to whether a properly mounted highlift jack ever become a 'missile' and caused injury or damage in an accident? If it has then it's probably not the right thing even if it may be a covered claim. I suppose an additional precaution would be to use a cable to lock the jack to the bumper. That would both act as a supplemental restraint as well as security. A lot of people mount a lot of different things to vehicles so that alone doesn't seem negligent. At least no more so than mounting 35" tires and a plate steel bumper with protruding recovery points.