livecd-tools was not requiring hfsplus-tools; this meant that generated images may not be Mac bootable, this package has to be in the live image build environment for the generated images to boot on Macs.
An update is already available that fixes this bug - https://admin.fedoraproject.org/updates/livecd-tools-18.12-2.fc18 . this bug is being filed for blocker/NTH accounting purposes. Proposing as a Beta blocker per criterion "The installer must boot (if appropriate) and run on all primary architectures, with all system firmware types that are common on those architectures, from default live image, DVD, and boot.iso install media when written to an optical disc and when written to a USB stick with at least one of the officially supported methods" in the case of Macs, for live images.
I was able to boot from USB stick created in livecd-tools on Mac Mini. hfsplus-tools was installed as an dependency.
Discussed at 2012-10-29 QA meeting acting as a blocker review meeting: http://meetbot.fedoraproject.org/fedora-meeting/2012-10-29/fedora-qa.2012-10-29-15.00.html . Accepted as NTH as it impacts testability on Macs. There was not clear-cut agreement for accepting it as a blocker with the few people in attendance, we decided to leave that issue open to save time; as it's NTH and a fix is available, it shouldn't be a practical issue, we will revisit it if it becomes one.
Update was pushed stable, closing.