i finally had a go at analyzing this common failure ...
the root cause is that the plastic part within the usb port has/develops a tiny amount of wiggle room. this wiggle ultimately causes the outer pins to snap off right in the "knee" of the "L" shape which attaches to the PCB.
you can replace the socket (it costs "nothing"), or you can solder tiny bent wires to it - i did the latter, and it actually worked (dunno for how long).
you will need a hot air gun, a preheating plate (the motherboard sinks so much heat that there is no way hot air alone will be enough), flux, and a little fresh solder. if you do the wire magic, you'll also need equipment for soldering tiny parts - a short-shafted pointy soldering tip (J shape), a magnifier, and a sufficiently steady hand.
you can try closing the gaps in the broken leads while the socket is still soldered, but i don't think it will work, as the solder is unlikely to flow that deep, esp. with the enormous heat-sinking of the PCB.