Odds are good that you've played a fair number of MMOs over the years. Every single one comes with a code telling you that it's very important you hold on to that code, that you need to keep a log of all your account information so that nothing gets lost. And if you ever lose it, you know that's an excellent reminder, since if you'd paid attention then
you wouldn't be sifting through your desk now
desperately searching for the notebook paper where you'd written your password.
Most players are fairly good about holding on to the important information for games that they're currently playing, but we can all get sloppier about former games. Have you ever wound up losing important information for your older games that forced you to buy a new copy or made resubscribing harder than it could have been? Or do you make sure to hold on to all of your information in a safe place, so that you can sign back up for any game at a moment's notice?