Do flat cables have any advantage over normal circular cables? I was looking at this.
6ft 2M Flat USB Sync Data Cable Charger Cord for iPhone4 4S 3G iPad1 2 3 Orange | eBay
A flat cable would probably have thinner wires, tending to be more fragile and poorer performing.
If you consider a circular coaxial cable it won't cause additional magnetic field to any point externally to the cable.