In iOS 7, Siri's voice is becoming less robotic and more human (we'll have to wait and see if she's more useful). One of those improvements will be how she pronounces names. Instead of butchering your name or choppily spelling out letters of your friends' names, she'll be able to be 'taught' what the correct pronunciation is.
9to5Mac found that Siri will ask for help in pronouncing names that she has trouble understanding when you say it the first time. If she doesn't ask for help, you can actually tell her how to pronounce the name and she'll try her best to say it like you. She'll show you different pronunciations and you can pick which one sounds closest to the correct one. From there, she'll always pronounce and understand difficult names right. Siri, she cares. [9to5Mac]