It's 1 a.m. on a clear night in New York. A taxi pulls up to one of the city's many nondescript concrete high rises. Erica and her two friends step out. Her cell phone beeps twice: "17C" reads the text. Inside the building, the doorman nonchalantly directs them to the elevator. As they go up, the music grows louder. The door opens slowly to reveal a scene that resembles a fashion photo shoot, with well heeled young men sipping martinis and mingling with model-types in an ultra-minimalist setting. As the party gets underway, Erica counts 12 people, including her and her friends. "It's never more than 12", she says with a smile...