This is a perfect example of Nintendo going out of their way to make things worse. I'm sure their intent was to create a safer online experience, but how does this system of per-game codes make things better?
I think the friend code system in general is not necessary. People should just accept an agreement saying Nintendo is not liable and be done with it. Then everytime you play an online game they give you a quick warning (much like the wrist strap) not to give personal info, be careful, etc.
...or Nintendo should integrate online options into their parental control feature. They could have an option to allow online games or not, then have several sub-options (allow chat, allow content sharing, etc.). There just has to be a better way then this hyper-protective friend code system.