Hosting a service at the level of security and availability required for an authentication system is no small undertaking, and Mozilla can no longer justify dedicating limited resources to this project. We will do everything we can to shut it down in a graceful and responsible manner."
I find this a bit confusing because citing low usage and lack of growth is something I'd expect to hear from a for-profit corporation, not a well funded non-profit. Have they shared information on how expensive it is to maintain Persona? I'm also unaware of any pledge drives to get funding for it.