It's funny, I've been thinking about this lately. In a vanilla relationship it's often a good thing to play it cool, not to reveal your hand too quickly, play a little hard to get especially if you're a woman. If you didn't you'd be considered unattractively 'in your face', gauche, maybe too needy.
But when you're a sub, these are unhelpful characteristics. You strive to be open, honest, revealing, responsive, pleasing; in short, vulnerable. Isn't it funny how one type of relationship requires you to hold back and the other to give all?
I think you can certainly feel needy about wanting a Dom/sub relationship in the first place, but, yes, once you have one and it looks like it's good for you, neediness is for those vanilla girls who don't know what they want, don't know how to ask for it, and never get it anyway. For a contented sub, vulnerability revealed to an understanding Dom is all she needs.