I successfully installed fedora-19-live-kde-x86-64 by USB key.
When I install DVD , after choose language, it has one more step to choose
install media, from sdb1(USB key ), iso image or network. It reported
the sdb1 not available , but the system is booting up by USB key, [so why?]
Anaconda explicitly refuses such a case:
https://bugzilla.redhat.com/show_bug.cgi?id=873647#c7
and also Comment 8 immediately following.
I believe that anaconda should accept it, but apparently this case
is one too many.