This will surely work for stopping online game piracy, but used online games will be as good as dead, as those voucher codes are only going to work once. After that, the game probably won't work on another system.
It has been a successful method of combating piracy on PC games. Most popular online games do have private servers, but the gaming experience on such servers are usually out-dated and have tons of bugs and lag. Even if an official server file leak is ever released for a game server, it would just become out-dated quickly and you wouldn't have the latest, nice features of the real servers.
Private servers are unreliable as they are hosted by small groups of everyday people. Private servers often go offline or disappear at any moment, so if you plan on investing time in ranking up or obtaining valuable skills or items you can kiss them goodbye.
I've played a fair share of private servers on the computer, and they are all like this. Private server gaming experience is just lame compared to the real thing. Quit being cheap and pay for it.
I honestly never buy or rent any game that has been opened, so this doesn't make a huge difference to me. But, if I ever had a thought about renting a game before buying, it surely is gone now.
This method is only useful for online play. If the code was verified locally (meaning unlock codes to play offline-only games) you could just patch it. But with online games it has to be verified by the server so you can't do anything unless you have access to the server.
I don't like this approach. They must be rather desperate to resort to this.