Current 3DS games have a max of 4GB (8GB later). Suppose you get a 128GB SDXC Card. With that card, you'd be able to hold over 30 4GB 3DS games. --- Camelot asked for your support of Golden Sun 4! http://ipetitions.com/petition/operation-sunrise/ "Why? Because of... DESTINY? PAH ha ha!" - Basilio
Just to clarify about security, too - jot down your 3DS serial number and keep it safe. Purchases are tied to the serial number and in the case that your 3DS is lost or stolen, Nintendo will use your serial number to give you your purchased games back.
Just thought I'd mention because I called Nintendo earlier about something and I mentioned that someone told me Club Nintendo was used to give purchased games back, and he corrected me and said Club Nintendo wasn't necessary at all.
Also asked about Nintendo Network ID and all that.