I was wondering why they were being selective on the people who could come to this. I really wanted to come and learn more about their API but it seems as though they were picking people who already built on it. Isn't the point of these events to get new people into the ecosystem?

To answer the question, yes people really do code and come up with solid apps at these events. Check out the music hackday apps that were built last weekend at the same space: http://wiki.musichackday.org/index.php?title=NYC_2011_Hacks