Jason, I didn't mean Macs are very likely to do such thing, just that they are mass production computers made with the same pieces as other major brands' PCs, so it's quite possible that eventually the USB circuitry of a Mac will misbehave and cause damage to one of our (well said) less than reliable external USB devices - not necessarily to all of our USB devices at once, neither to more than one. And I brought the exemple of what just happened to me.
Apple, Dell, Asus, HP, Toshiba, you-name-it, none of their consumer systems are failure-free. Same for the USB DAC boxes and wireless transceivers. If they were, we couldn't afford to buy one. There's a long-lasting discussion over dead pixels on consumer LCD panels (which afects the works of designers, photographers) that pretty much illustrates this: zero dead pixel panels are available, indeed, they are needed in the medical field and cost over $5,000 - from the same makers of cheaper consumer LCDs, making it very clear that near perfection quality control standards means a huge cost and that's why regular, affordable consumer products don't have it.
Bottomline was (and still is) that one should not make the assumption Macs are failure-free. No, they are not. There is just too much technology built in new computers and other digital devices for the price. Of course, quality control is more loose than we'd like.
Regards, Bruno