Currently we have almost 90 active mirrors in the official mirror list and new requests for becoming an official mirror are appearing quite often. However, not all mirrors are good ones (outdated, incomplete, admins don't respond, etc). I marked inactive many of them during past months (including about 20 during FrOSCon), and will continue to do this until all of the mirrors meet the requirements.
22 mirrors that are in the official list did not move to the 2-tier scheme yet, which means we do not know where do they sync from, admins did not respond or there is no known email address of the admin. These will be removed from the list very soon. If you are using some mirror that was removed from the list recently and you know how to contact the admin - let me know.
Considering the fact that there is no package signing support yet I don't see a reason why we should have that many mirrors, especially when they don't meet the requirements.
Recently I had to defer some requests to become an official mirror from some private sites. I apologize that this caused a frustration of their admins and hope that the reasons are understandable.
To make this fair to everyone I'm thinking about (temporary) putting the process of adding new mirrors on hold.