All Blu-Ray discs are coated with a protective coating which prevents stratches and fingerprints. The most highly marketed version of this coating - TDK's
Durabis has been able to sustain attacks by a screwdriver and steel wool. While I don't believe Sony and Panasonic (both Blu-Ray duplicators) are using Durabis, they are using something very similar. While not the 100% protection that cartridges provide, it does a damn good job and keeps discs costs down.