With this in mind, i've written a little init.d script for my ROM which backs up the EFS partition on boot if a backup does not already exist. A non intrusive safety net for users if you will.
The script just needs a suitable boot image that runs init.d, although it could easily be tacked onto the end of install-recovery.sh if that's not the case.
I'd love to encourage all developers to use this script for users' sake!
You can download the script here - http://cl.ly/2j0p0R3F07052m2T2u0e - but it's very simple, here's the code...
#!/system/bin/sh # EFS auto backup script for Samsung Galaxy S II # By @paulobrien - http://s2.MoDaCo.com mount /dev/block/mmcblk0p11 /sdcard if [ ! -f /sdcard/efs.autobackup.img ]; then dd if=/dev/block/mmcblk0p1 of=/sdcard/efs.autobackup.img fi umount /sdcard
Note the manual mount / umount of sdcard is necessary because this happens late in the boot process.