In this case, it's not so much that it's some big top secret thing, but that it genuinely is something friends invite their other IRL friends to. I brought it up because it was relevant here, but it's not something exactly advertised. As a practical matter, the facilities can only host a specific number of people, and it's already the case that there's always a waiting list for tickets.

(It's not directly a Burner event either, although with a lot of East Bay attendees, there's organically a large portion of people who go to both.)