[mikeash]

Sure, but the magnitude of that cost matters a lot. You were saying a dollar or two in raw materials to protect against 100W, now you're saying three or four cents. A few cents to protect hundreds of dollars in equipment from electrical faults seems worthwhile to me.

[teraflop]

That makes sense from the consumer's point of view. But imagine you're a manufacturer, producing USB device controller chips by the million. Would you really be willing to spend tens of thousands of dollars to protect against a failure mode that can only happen due to some other company's extreme negligence?

[mikeash]

Yes, but of course it doesn't matter what I think.

It's not abnormal to add protection that isn't needed when everything works properly. As noted elsewhere, the USB spec already requires resettable overcurrent protection, for example.

[knughit]

Tens of thousands of dollars total is far less than it costs a company just to moot the question.

[krapht]

Sorry I was not clear in my comments. The dollar solution is for some type of crowbar circuit. This is the most robust solution.

The 3-4 cents is for specifically, reverse polarity protection when somehow, a -5V differential is applied to device power inputs.

This cheaper solution only narrowly addresses this particular power fault, and no others.

[mikeash]

I see! A dollar per port for robust protection against a wide variety of faults sounds pretty good to me, but I know that sort of stuff doesn't sell well when people compare primarily on price.

Do I assume correctly that a fuse for overcurrent protection wont act quickly enough to save the hardware in the event of reverse polarity?