I watched a great documentary on the subject, unfortunately I can't remember the name of it. However the doc focused on a group of programmers who were working in cryptography and sharing messages on public boards.

They narrowed it down to 2 out of the 6, and they said that it was either the English guy or the American, but most likely the English one.

I like the fact that it's a mystery, he remains a legend; his name becoming like that of Robin Hood :-)

Cg