You bring up quite a few excellent points, re: OEM engineering versus shade-tree tinkering. There is definitely merit to considering the "brain" of a car to be

You bring up quite a few excellent points, re: OEM engineering versus shade-tree tinkering. There is definitely merit to considering the "brain" of a car to be integral to its safety. Should a person wish to modify their car from OEM specifications, there are numerous avenues by which this can be done in a negative manner. As a reference point, I've been a "car guy" and fan of tuning / customization / tinkering for over a decade, and even had a chipped turbo car at one point in my life. Regarding a real-world hazard specifically, I'll cite the example I frequently see on the road of a Chevy/GMC/Caddy SUV with much larger than stock wheels and tires and bone stock brakes. This is an obvious violation of the OEM engineering, a genuine physics problem. The safety of the driver/passengers is in jeopardy, as is the safety of others who share the road. Thus, I'd like to note that I believe there's a bit of self-serving "caution" in place when it comes to manufacturers. I'll be stating a far-fetched sounding hypothesis, but one I believe is relevant. Okay, so if a manufacturer sells a car, but with extensive restrictions on modification, why does the manufacturer simply get to "write-out" safety obligations for the lifespan of the vehicle? Sometimes there are "service plans" that will address some basics (oil, tire inflation), but only for a limited timeframe. Should OEM safeguards to computer systems only apply for that period of time? Or, to put it another way, if manufacturers cared about safety, why wouldn't they be held responsible for performing State Safety Inspections and provide the materials to ensure a vehicle meets the safety regulations year after year after year? I know this is an out-there type of postulation, but when talking about vehicle safety, there are many factors that are much more practical in nature (maintenance, driver distraction, age-related degredation of faculties) that get little to no discussion because they're difficult problems. I'm mentioning this notion as a direct response to your theory that "companies are right in making the cars impossible to tweak" because, practically speaking, that's not the case at all...I see this discussion as many trees in the forest of motoring...