The breaking-axle incidents have happened after 80,000 miles, the majority coming after the six-figure mileage mark. Ford's take is that nearly all drivers have retained control of the vehicles, and the few that haven't have described behavior that doesn't fit with Ford's predicted vehicle behavior in such an incident. Therefore, it isn't a problem with safety.
As for the NHTSA, even though the complaints are spread over various categories (consumers choose their own categories under which to report), it says it has reviewed every single one of them and says it is monitoring the situation. We suppose everyone is relying on good judgment to decide when or if to declare this a safety matter and open an investigation, and we can agree with that – good judgment can make far more sense than trying to slap hard numbers on these kind of occurrences. The question is: Who's the one with the good judgment?
UPDATE: A new report by USA Today states that NHTSA has officially launched an investigation into this problem, which accounts for nearly 1.5 million Windstars that were produced between 1999 and 2003. NHTSA has received 234 different complaints about rear axle failure, 55 percent of which say that the rear axle fractured completely, while the remaining 45 percent say the axles broke while traveling at speeds of 40 miles per hour or faster.
Two accidents have been reported due to this problem. In one case, the driver says that the axle "snapped in half" after the vehicle ran over a pothole, causing the rear tires to blow out. The driver of this Windstar struck a guardrail while trying to stop. The other instance happened under similar circumstances, and the driver hit a curb at low speed while trying to stop the vehicle.
NHTSA states that the Windstar uses a beam-style rear axle, and that these problems could be caused by road salt collecting on the beams, causing corrosion. Both instances are reported to have occurred in "Salt Belt" states. Ford says it is fully cooperating with the investigation.
[Source: New York Times, USA Today]