Today’s xkcd suggests geohashing – using the date and Dow opening to generate a random physical location for a meetup. It’s fun to think about this method being used to coordinate Ephemerisle gatherings. I can see the method being both better and worse on the ocean because of it’s relative homogeneity – every place is like every other place. So you don’t have the failure mode of randomly generating a location that’s difficult or impossible to reach, but you don’t get the excitement of generating a location that is challenging and fun to get to.
The cryptographic aspects are fun: if only some people know the formula (or the salt), then you get a secure method of generating festival locations where nobody knows the location in advance (you need the Dow opening), and only some people know the location once all the information is available. Those could be good properties for a festival – although it’s not like you can hide from satellites. Or can you? Ideas?