1.4mm Thick Gigabit Ethernet Cable
TheIonix writes "Flat network cables aren't anything new, but I'm pretty sure ones like this are. Japanese accessory king Elecom today announced the "LD-VAPF/SV05" network cabling, coming in at 1.4mm thick." Also here's their press release if you can read Japanese.
Most of the thickness of standard Ethernet cabling is not the metal wire but the protection of that wire from EM radiation and physical damage. This ulti-thin version might not be able to withstand those conditions which could result in data corruption or loss.