video on demand$ diskutil list
Figure out what your USB device is called with mount or sudo dmesg | tail (e.g. /dev/disk1) and unmount the partitions on the device (i.e., /dev/disk1s1) while keeping the device proper (i.e., /dev/disk1):
$ diskutil unmountDisk /dev/disk1
Now we can continue in accordance with the instructions above (but use bs=8192 if you are using the OS X dd, the number comes from 1024*8).
$ dd if=image.iso of=/dev/disk1 bs=8192
20480+0 records in
20480+0 records out
167772160 bytes transferred in 220.016918 secs (762542 bytes/sec)
It is probably a good idea to eject your drive before physical removal at this point:
$ diskutil eject /dev/disk1