The real question is: Does ANYONE know who he is, or is he truly anonymous? It's conceivable that his family, co-workers, or project contributors know who he is; it's also believable that he is the only one who knows his identity. I can imagine LOTS of people developing software and working on a project where no one else really knows what they're working on.
C'mon, seriously? The core developers know who he is. The first venture capitalists know who he is. Ask Andreas. Ask Gavin. Ask Garzik.