Why do these people become stars? Economics suggests it's because they're already proven to some degree; eg. http://www.overcomingbias.com/2009/04/why-not-superstar-slav... summarizes a Tervio article predicting superstardom when the following conditions are met:

    Desired abilities are rare and lasting.
    It is very expensive to try someone new.
    Everyone can see which trials worked or not.
    Winners are free to demand more money or walk.

#1 is arguable whether it's true, but people seem to think it's true - any endeavour by someone like Rose comes with built-in interest & buzz. Why? Personal affection? No, because people think it's better than a random newly launched project. #2 is fairly true - how do you test someone on whether they can build a successful Facebook clone or innovate on it with less than thousands of dollars of their time and other resources (at a minimum)? #3 is pretty true, especially for web communities. #4 is very true; as Hacker News people love pointing out, it's a free country.