The point in general for holding purchasers liable is maintenance traditionally for 'wear and tear' as opposed to defects. To use a car analogy if your car get

The point in general for holding purchasers liable is maintenance traditionally for 'wear and tear' as opposed to defects. To use a car analogy if your car gets into an accident because the break pads should have been replaced 10,000 miles ago that is your fault. If it is because the break pads disintegrate if they get wet that is the manufacturer's fault. These aren't cars however, but it does bring to mind a hypothetical consistent set of standards involving patches. So if say the product was perfectly fine at launch on 32-bit platforms but it has a bug when run on 64-bit platforms it would become the user's problem. It obviously wouldn't be a very good system, it isn't realistic in its expectations nor easy to judge or administer with all of the nuances and fine details of knowledge.