I feel like you're on to something here. I've observed the same pattern in video game design workshops and in hackathons, so I'll go one further and say that those things have "magic circles" as well. The biggest challenge in the hackathon community is how to make projects last beyond the hackathon. Likewise, games designed as part of courses or workshops (I've been a part of several, including at #hack4missions at Urbana 15 and as part of Video Game Studio at Northwestern) don't tend to make it off the ground - the ones that do are the rare exception. The person who answers the question of "how to take the hackathon home with you" will be heralded as a genius. So far, the only thing that seems to work is knowing the people you group up with before you get to the event, since that makes you stay in contact in a non-forced manner afterwards. For that reason, I always like to go to events with at least one person that I know - at a minimum, it gives me the chance to talk about the shared experience.