Whacko problem of the day:
It appears that MoCA (network-over-TV-coax) hardware is so good that it can actually communicate wirelessly over short distances, accidentally, via crosstalk between unconnected cables. In apartment buildings, it's possible to actually connect to your neighbour's network by accident, or bridge your two networks together.
100 MBits/sec, apparently.
Come on, physics. Cut us some slack here!