I doubt the OP is a celebrity to worry about data privacy Have there been any cases of data going missing on cloud storage? As @avi says, cloud storage operators do all the work figuring out data redundancy.
SD cards use similar NAND flash as on SSDs. However considering they cram so much data in such a small space, the quality of such NAND will be far inferior, not to mention they could be using TLC. Data retention was already an issue on inferior NAND like on the 840 Evo. I suspect SD cards might have the same problem.if data is so very important.. just invest some money and buy some 128 G sd cards