I don't think you understand the point of this. It will allow you to create read only USB drives. This means that people who work on computers all the time now don't have to haul a case of CDs around because viruses could possibly jump onto their read-write thumb drive. They can now setup a thumbdrive with all their tools and it's "read only".

$ cat /etc/fstab

/ /dev/sda2 ext4 ro 1 1

That really doesn't protect the device from an infected system - it can just remount it rw. You need a hardware write blocker to protect against a malicious system.

You don't need a hardware write blocker, the beauty of "burning" an ISO to a thumb drive is that the ISO format doesn't allow writes. There is no way at all to write to it unless you rewrite the drive itself in which case it becomes fairly obvious.

http://unetbootin.sourceforge.net/ automates the process.

I thought unetbootin was targeted towards single partition drives? The main advantage of what I've written is you get a nice FAT32 partition with syslinux, and secondary partitions on your USB drive for the actual OS; thus Windows (dunno about Mac) can use the drive normally, and it doubles as a bootable drive. Unforutnately unetbootin's "how it works" page is extremely sparse on detail. http://sourceforge.net/apps/trac/unetbootin/wiki/howitworks