I have swap on the SD card. I just pulled the cover and my SD partitions got unmounted EXCEPT for the swap (which is not really mounted). I guess, but I cannot confirm, that when pulling out the cover any mounted partition (perhaps even only VFAT, but I don't know) gets unmounted, but that's all. Swap is by definition not a mounted partition, so nothing happens. Obviously, if you do pull the CARD with swap on it you get an instant crash.