While trying to transfer loads of stuff from an old Mac to a new one via FireWire Target Disk Mode, for some reason the target Mac just would not mount on the desktop of the new Mac. I tried everything: different cables, different ports. I checked other computers -- they worked correctly. I even tried mounting the new Mac on the Old one -- that worked, too. But using the FireWire cable, the old Mac would not even show up in Disk Utility or Terminal.
On a whim I decided to hook up an external FireWire drive to the new Mac, then daisy-chain the old Mac to that drive. Presto! It worked, and it seemed to be just as fast as a direct connection.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20070813144523110