There is no legal free support in Linux or OSX for FAT16 (MS patents, I'm told). That makes the built-in SD card reader of little use on the MBP. If you insert and try to use a FAT16 sd card OSX will eventually fsck up the filing system and mark it "dirty" even though it isn't. Even Terminal can't fix it after that happens. The usual fix is to put it a camera and reformat.
I went to CompUSA and bought a $10 generic USB card reader and put a SanDisk sd card the internal would not read and in the external adapter it would allow me to read/write/format. Fvck you MS, and Apple, too. If I can do it in an external and not the internal without any extra software, both of you svck.