its worth knowing, but to me personally if someone gives you a code before you had done anything for them, then they are either very trusting or its a scam.
when it comes to codes, there is never and easy way to get them. best thing to do is buy them from a legit store.
however lets say you bought a code from a reputable online retailer, and then that code gets ''lost'' in the post and you get your money back or a replacment. would that first code still work if it then got ''found''? and i guess that works for wii and xbox points too.