Thanks in advance for your opinion. I have an external hard drive and a time machine for backing up my files. The external hard drive goes in my safety deposit box so if my house burns down with my computer and time machine no big whoop. Was thinking of putting my macbook air SD card slot to use by getting rid of the big external hard drive and putting my backup files on a 32GB SD card. It seems to me that I can put any file I want on there including Word docs; however, when I shop around to buy an SD card, the advertisements and reviews only talk about storing pictures or video on these cards...is it okay to store documents and other non-video or non-photo files on the SD card? Am I missing something here? Also, if I can go ahead and store my docs on the SD card, does anybody know the difference between Class 4 and Class 10 and the speeds and which card you might suggest I get for backup?...need a little expert direction here....thanks!