SDs can fail definitely, they're flash memory devices. Flash storage can and does literally wear-out after an X number of write cycles. Writing to EEPROM (electrically erasable programmable read-only memory) is actually destructive, and can only be done so many times. Internal flash storage on a phone can fail as well, however it's much cheaper to replace a failed/worn-out SD than it is to buy a new phone. Something that can happen with them, they'll go read only, which is them detecting that they're failing and switch to read only mode to try and protect and preserve the data already stored on them, so you can hopefully retrieve it. USB flash drives and SSD drives can also fail/wear-out in the same manner.