Most of the aircraft you all fly on have electronic throttles as well as electronic fly by wire with no mechanical back-ups. However,there is a significant level of redundancy in those systems. When I scanned my Saturn Astra which is Throttle By Wire (TBW) I was reassured to see that the gas pedal and TPS systems were dual channel systems. Much like a modern FADEC on a jet engine. In Fadecs, the throttle lever positions are only allowed to deviate a certain amount from each other. This and the fault handling response is handled in software as well as an arbiter model to help determine which channel is correct based upon engine RPM, and MAP. I would hope that this same logic would be applied to automotive applications. My first thought would be when the channel disagree exceeds the limits, the arbiter model is used to select the properly functioning channel, failing that, the throttle would be reduced to idle. This could be dangerous on an interstate and cause serious accidents as well. There is no way I would trust a single channel throttle system in anything. Cruise control is easy to implement in these systems since it does not require a separate servo actuator as in the old days. Traction control, torque limiting, linearization, and other driveability enhancements are easily implemented in TBW. Really it all depends on the vulnerability of the hardware to a single point failure or disturbance and the level of sophistication of the software. Reducing the throttle to idle on brake application would be easy to impliment in software provided the FMEA says its the safest thing to do for all situations, provided the throttle servo is operational and the butterfly is not stuck (no butterfly on direct injected engines). You could always do a fuel cut as well. Sorry for being long winded, but I love engine controls AND I just bought a new Tacoma (manual trans).
Note that direct injected engines are becoming popular now. They have no throttle plate to move so TBW is about the most practical throttle control. With regards to electrical noise causing the malfunctions, the automotive manufacturers also subject their vehicles to pretty harsh EMI testing from both internally generated and externally generated (i.e. lightning, cell phones, etc...). For the event vehicles, I'd like to see the data from the vehicle event recorders that are being installed in cars/trucks now. These are similar to flight data recorders. You can bet that toyota seized these out of the accident vehicles to try to figure out what happened. There is a little blurb in my toyota owners manual about when and how this data can be used and who can have access to the data.