I have fine, thin hair as well, and I kept it long through my teens and early twenties. It did absolutely nothing for me. Then I saw Sliding Doors and got Gwyneth Paltrow's pixie blond cut...super short in back, long in front. People would compliment how European I looked.
Plus, I had a great style for formal hair...as she did in the movie, I twist my hair up in flowers for every formal event. It kills me when people ask who did my hair, and where they can get such professional and stylish results. Even my hairdresser couldn't style my hair the way I can, but she did one heck of a job cutting it.
I had a boyfriend who was wildly insecure about dating me, and who was also a real jerk. He was cut loose shortly after he suggested I grow my hair out. Turns out in his hometown, everyone had long hair (yes, and puffy 80's bangs) and he was one of those men who thinks long hair is better regardless of what type of hair you have, etc.
Thank goodness my DH has better sense (and a much more updated sense of fashion!)