Two problems related to brake disc pads have been reported for the 2006 Toyota Prius. The most recently reported issues are listed below.
Failure if the abs brake actuator after 105,000 mile in February 2019. The actuator would run every few seconds while the vehicle was on causing the the rotors and brake pads and trims to heat up excessively. This is a well known and documented problem with generation 2 Prius.
Total loss of brakes while driving on highway. Passed through red light near miss situation. Towed to shop and cost of repair exceeds $2000 for this involved repair as this is a complicated braking system. Part of the abs system called the accumulator is defective in these cars and can result in spontanious brake failure. You are always supposed to have some braking even if the assisted brakes malfunction. Suddenly, our car had no brakes at all. My wife was driving the car when the brakes failed. She had zero brakes from the pedal and the peddle style emergency-brake had locked up and or wasnt enough to stop the vehicle. She nearly had an accident. Braking system should not give out on a vehicle that gets very little wear to the brakes due to the extra regenerative braking system. Our brake pads and shoes have lots of life still. This is purely a design flaw in the braking system and I believe these vehicles are a hazard on the road. I have loved the car until I experienced this brake failure.