As an attorney, reading this question invokes the same reactions that many of the /. crowd would have if I started trying to opine on the technical failings that would allow our mythical vandals to reprogram the hypothetical robot.
Not to get too technical, but just because you sue the company doesn't mean you win. The liability insurance that even the smallest companies carry would cover the legal costs of having such a suit dismissed. (For the technically inclined, look up comparative negligence and the proverbial "intervening bad actor").
The homeowner (the ones suing) would probably be found more responsible for not following basic security etc.
As others have pointed out, software companies have long been given practically a free ride in harm caused by poorly written software. First, they have been allowed to disclaim the standard warranties of fitness and function. This is akin to buying a car that the manufacturer won't promise to actually work or be safe. If Ford told you that they wouldn't guarantee that pressing the brake pedal actually engaged the brakes, would you drive that car? Yet every piece of commercial software we use specifically says that there is no promise that it will work at all, or do what the purchaser wants.
Here is a counter hypothetical (more realistic as it has actually happened). A relative dies in a plane crash. The FAA investigation conclusively shows that the accident was caused by a bug in one of the key computer systems. Should you sue: the airline? The manufacturer (boeing/airbus)? The subcontractor that wrote the software?
The answer is, you sue the airline, and the system is set up so that anything you win from them, they can then sue to recover from the party up the chain. Thus, everyone's liability is ultimately apportioned according to their degree of fault (note, yes it is a gross simplification). This is why people writing software for critical systems (ones where a failure can cause property damage or injury) need a good lawyer to write their contracts/licenses. They law has allowed programmers to avoid their responsibilties for a long time, so if a sw company doesn't take advantage of that, it is their own fault.
Consider, there is no educational or professional certification required to write and sell software that controls an infant incubator used in an NICU, but you need a government license to drive to the store. Programmers and engineers have been getting a sweet deal in liability for years, so it's awesome to hear them still complaining.