SD cards are not a secure floppy replacement: They include CPRM with device revocation. The "Secure" in "Secure digital" means "Secure from the user," not "Securely holds your data."
Yes, the write protection switch may help you avoid accidentally deleting your keys. Also blocking some virus from getting onto the SD card.
You missed his point. Just like DRM is a euphemism where the R stands for Restrictions rather than Rights, SD cards are securing the industry from the user. Some Windows smartphones will lock-in SD cards. That means after a single insertion into the Windows mobile based phone, they are *completely inaccessible* on *any other device*.