Piping dd over an SSH connection

Picked this one up from the K12LTSP mailing list. You can pipe dd from one machine to another over SSH, like so:

dd if=/tmp/somefile |ssh root@target_machine dd of=/tmp/someotherfile

In the message, it was being used to transfer a whole partition from one machine to another thusly:

dd if=/dev/sda |ssh root@target_machine dd of=/dev/disk_name