I didn't write this to comment to "knock the author down a peg". From the facts of the story, my sympathies totally lie with the author. But the way he comes off is as entitled and arrogant. There is no reason that I can't feel that Billy was in the wrong, but I also dislike the author's attitude.
Entitled to what? Entitled to ownership of IP he produced? Entitled to the 0.4% equity stake that they agreed upon at the beginning?
The backlash in this thread is mindboggling. The author's "attitude" seems pretty appropriate for someone who was very recently betrayed by a team member. I understand if you don't like the "nerds vs jocks" imagery but frankly that's not arrogance, it's colorful storytelling.
I agree with you, what did the author think was going to come out of a Startup/hacking weekend? You are basically giving away your talents at those events. One has to manage expectations better, and also avoid the Billys of the world.