As one bearing the name of Stephen, I have read a little etymology and it seems that many people try to answer the question by pointing to the Greek Stephanos, which is incorrect because the question is asked of English, not of Greek. Was there not a Norman King of England, Stephen, whose court spoke French? Could there be a precedent in old Norman for the use of ph in the name? As well, the biblical saint, and first christian martyr, Saint Stephen, is ALWAYS pronounced the way King Stephen, and Stephen King, are pronounced. Stephen's Green in Dublin and almost all uses of Stephen in Ireland, follow the English standard, not the Scottish (v) usage (like Robert Louis Stevenson). So the pattern of Stephen is historically, biblically, and descriptively pronounced as Steven and not as Stefan, although I grew up with a Polish lad, Stephan, who prounced his name as Stefan. So it all depends on your preferred national standard. I'm sticking with King Stephen and Saint Stephen, thank you very much.