Here's an excerpt from the announcement:
The new Fedora Commons Wiki provides a stable environment for developing Fedora software, documentation and communities. The new wiki features additional personalization and development tools for communication and tracking including a feature long-requested by the community–automated account registration with "Capcha." So it’s easy to join our community while making it difficult for spammers.
Please note that you do not need an account to read the Fedora Commons wiki—it’s open to everyone. You must register at the new wiki, however, if you want to add comments, articles, ask for help, or participate with other members of the community.