Is it a good thing that people can come back with their memory cards and keep playing the game? I could see people just buying the card and standing there and play all day (of course you can kick them out, but they probably would raise a tandrum before allowing you to do so...).
I could see that being a good use: certain new contents would be a certain stores, so you have to go to that store to get it (and lure you to buy stuff of course).