Could Toyotas speed problem be located in the cruise control?

I have given some serious thought to the problem with some of Toyotas vehicles abruptly speeding up and out of control. my theory involves the vehicles cruise control. ever been in a situation, where you were using your vehicles cruise control and approached an uphill grade? your gas pedal suddenly goes to the floor in an attempt to keep your vehicle at the preset cruise speed. sometimes, a transmission will automatically downshift in order to compensate for the lost speed and this throws your vehicle into a speeding condition, to catch up. what if Toyotas cruise control was defective, even on level ground and sent a vehicle into passing gear on its own, causing the fast speed and out of control? it would interesting to know if all the Toyotas involved had cruise control on their vehicle.