Hey there,
I don't know if that statement about identification of religion by surname can really be asserted confidently. I think there are some religions in which name changes may occur, but generally it is the first time that seems to give the faith of one's background away.
Is there a need for atheists to identify themselves as atheists without expressing it openly to the world? For some religions I can see why one would choose a first or last name to pay homage to their faith, but that doesn't seem to be a priority if one is atheist...