The VP8 plugins where moved to -good from -bad for this release, but it hasn't been built as part of current package.
gstreamer1-plugins-bad-free-0.11.99-1.fc18, gstreamer1-plugins-base-0.11.99-1.fc18, gstreamer1-0.11.99-1.fc18, gstreamer1-plugins-good-0.11.99-2.fc18 has been submitted as an update for Fedora 18. https://admin.fedoraproject.org/updates/FEDORA-2012-14426/gstreamer1-plugins-good-0.11.99-2.fc18,gstreamer1-plugins-bad-free-0.11.99-1.fc18,gstreamer1-plugins-base-0.11.99-1.fc18,gstreamer1-0.11.99-1.fc18
Package gstreamer1-plugins-bad-free-0.11.99-1.fc18, gstreamer1-plugins-base-0.11.99-1.fc18, gstreamer1-0.11.99-1.fc18, gstreamer1-plugins-good-0.11.99-2.fc18: * should fix your issue, * was pushed to the Fedora 18 testing repository, * should be available at your local mirror within two days. Update it with: # su -c 'yum update --enablerepo=updates-testing gstreamer1-plugins-bad-free-0.11.99-1.fc18 gstreamer1-plugins-base-0.11.99-1.fc18 gstreamer1-0.11.99-1.fc18 gstreamer1-plugins-good-0.11.99-2.fc18' as soon as you are able to. Please go to the following url: https://admin.fedoraproject.org/updates/FEDORA-2012-14426/gstreamer1-plugins-good-0.11.99-2.fc18,gstreamer1-plugins-bad-free-0.11.99-1.fc18,gstreamer1-plugins-base-0.11.99-1.fc18,gstreamer1-0.11.99-1.fc18 then log in and leave karma (feedback).
gstreamer1-plugins-bad-free-0.11.99-1.fc18, gstreamer1-plugins-base-0.11.99-1.fc18, gstreamer1-0.11.99-1.fc18, gstreamer1-plugins-good-0.11.99-2.fc18 has been pushed to the Fedora 18 stable repository. If problems still persist, please make note of it in this bug report.