This was achieved w/o much trouble using my FreeBSD server at work. I performed the following operations logged in as root.
The USB image was downloaded from the PC-BSD website
Assumption: the USB memory stick is plugged into the server at /dev/da0
# fdisk -BI /dev/da0
# bsdlabel -w -B /dev/da0s1
# newfs /dev/da0
# dd if=/usr/home/kengell/PCBSD7-x86-USB.img of=/dev/da0 bs=1m