Yeah, when I was in elementary school I was still on the "Wait, why is it SHAWN when it looks like SEEN?" page :) I think a lot of people leave out double letters accidentally. I get "Ema" way more often than I'd expect.
Oh really, I've never had my name spelled Ema (thank goodness!)And I do agree with you about Sean. Especially with Sean Bean - it looks like it should rhyme!