The USB 1.x and 2.0 specifications provide a 5 V supply on a single wire from which connected USB devices may draw power. The specification provides for no more than 5.25 V and no less than 4.75 V (5 V±5%) between the positive and negative bus power lines. For USB 2.0 the voltage supplied by low-powered hub ports is 4.4 V to 5.25 V.
A maximum of 5 unit loads (500 mA) can be drawn from a port in USB 2.0, [...]
If the USB hub was operating according to spec, then it really is rated for no more than 5V and 0.5A per port (for devices transferring data, anyway; there're other specifications for things like using the USB port for power-only). If it melts down because a mini-fridge was plugged in to it, that's hardly its fault.
It does look like a POS, in that it doesn't seem to have any decent form of over-current protection on any of the ports, but almost all USB hubs out there don't have any either.
It is likely D-Link just threw in a generic 7-port USB hub, put their label on it, and sold it for a nice price premium. Unless there's good evidence that the manufacturer did something special with their circuitry, chances are it's no better off compared to a generic USB hub that costs less than half the price.
I'd be careful plugging in
anything with a high power draw to a USB hub (unless it's self-powered or has its own AC adapter, and uses USB only for communication). Chances are it's operating out of USB spec and might kill your hub. The USB port and cables were not conceived or designed for high power delivery, I'd use a more appropriate cabling system for that.
If that's not what caused the burst capacitor, you really should write in to D-Link with a complaint.
