I have noticed the following problem using bind mounts: I have an encrypted disk which I mount at "/media/crypt". The disk does in particular contain my home directory. Since I would like to access my home via "/home" I used a bind mount like so:
mount -o bind /media/crypt/home/ /home
After that, "ls /home" gives me the home directory "username". To make this permanent I added
/media/crypt/home /home bind defaults,bind 0 0
to my /etc/fstab. Unfortunately once I restart my system and type "ls /home" I get a new "home" directory, in total "/home/home/username" instead of "/home/username". So apparently systemd mounts "/media/crypt" on the mountpoint "/home" instead of binding "/home" to "/media/crypt/home".