I'll add in my recent experience with a complete brake failure - 2003 Limited V8 with 150,000 km.
Was driving in city traffic when the brake warning (red) indicator lit up on the dash. I did not notice any major difference in braking power the first few stops after this indicator came on.
Then as I continued additional warning (orange) indicators lit up - I believe they were the ABS, TRAC and VSC - accompanied by a high pitched audible warning.
When I went to depress the brake pedal, it went to the floor with little resistance. As I was approaching stopped traffic, I had to quickly take evasive action by changing lanes and then bailing into a nearby parking lot - all the while applying the parking brake during this emergency.
Fortunately, the parking brake did eventually bring me to a complete stop. I was able to avoid contact with any other vehicles or pedestrians, and no body damage was done to my T4R.
Shaken by this experience, I immediately called my local Toyota dealership. A towing company came to the parking lot and using a flatbed my T4R was brought to the dealership. While waiting for the tow, I looked under the hood and observed the brake fluid reservoir to be completely empty - had been fine the last time I checked it.
Once up on the hoist at the dealership, the cause was found to be a failed brake line just above the rear axle on the driver's side. Cause of the failure was attributed to corrosion (we use a lot of road salt up here during the winter).
My T4R is still at the dealership awaiting the arrival of new brake lines.
Returning home, there was no evidence of any leak in the driveway from the area that the brake line failed. Thus, a catastrophic failure!