SD Card Pin State During Hot Insertion
Hot insertion on a shared SPI bus won't work at all with SD cards. One must remember that SD cards come up in SD mode, where the CS is active high. 

You need to explicity switch the card to SPI mode before you can use other devices on the same SPI bus, this is obviously not possible when you insert a card during another SPI transaction.

Either use a bus driver chip to connect the SD card or use a different SPI bus, for example software SPI using GPIOs.