I recently bought a 5m VGA cable (for a wall monitor, mounted on a long swivel arm with gas struts). It's short enough for the video signal to go through, but too long for the EDID to be readable, so it can't use the monitor's native resolution.
Also bought a 5m HDMI cable, but that one didn't even make it to me. It got wrecked in transit and returned to seller. Fortunately I got a refund.
edit: unexpected HaD jolly wrencher.