Diane, contrary to popular Starbucks opinion, is not a substitute or nickname for Diana. It's not shorter or easier to write. It's just completely different!
I mean "Diane" implies I own a Kate Spade briefcase. Maybe I have my hair styled every other Friday. Or a car that I drive only on weekends. And definitely a space in between my teeth. Would Diane even order a Light Java Chip Frappachino? Ummm I don't think so.
Perhaps my biggest fear though is that Starbucks prefers the fictional Diane to the regular Diana. I mean, I pronounce my name clearly when it's my turn at the register. So I think what Starbucks is really saying is, "Hey, we'll be honest. We know you said 'Diana.' But we'd rather make this drink for Diane. She works so hard to afford that weekend car. She needs this."
Whatever, Starbuck. Yeah, that's right. Diane might not get your name slightly wrong, but Diana sure will!