The missing link:
http://wdc.custhelp.com/cgi-bin/wdc....i=&p_topview=1
And the text:
The following external hard drives are bootable on Intel-based Macintosh computers systems through USB:
My Book Essential Edition
My Book Essential Edition 2.0
My Book Home Edition
My Book Mirror Edition
My Book Office Edition
My Book Premium Edition
My Book Premium Edition II
My Book Premium ES Edition
My Book Pro Edition
My Book Pro Edition II
My Book Studio Edition
My Book Studio Edition II
My Passport Studio
The following external hard drives are bootable on Intel-based Macintosh computers systems through FireWire (1394a/b):
My Book Home Edition
My Book Mirror Edition
My Book Office Edition
My Book Premium Edition
My Book Premium Edition II
My Book Pro Edition
My Book Pro Edition II
My Book Studio Edition
My Book Studio Edition II
My Passport Studio
The following external hard drives are bootable on Power PC based Macintosh computers systems through FireWire (1394a/b):
WD My Book Premium Edition
WD My Book Pro Edition
The following external hard drives are not bootable on Power PC based Macintosh computers systems through USB/FireWire 1394(a/b):
My Book Essential Edition
My Book Essential Edition 2.0
My Book Home Edition
My Book Mirror Edition
My Book Office Edition
My Book Premium Edition II
My Book Pro Edition II
My Book Studio Edition
My Book Studio Edition II
My Passport Studio
My Passport Elite
My Passport Essential
WD Passport
WD Passport (Silver)