Thematically, we're choosing Water as our vehicle - riffing on the fact that half the world's population does not have reliable access to clean, potable water.
Participants in the game will be issued an empty water bottle at the beginning of the game; for the entirety of the ARG, they will not allowed to drink anything except what is filled in the bottle by redeeming Potable units they earn through various tasks around the Long Beach area (obviously, we are on the honor system here! :) ).
Everyone will be issued a small supply of cards, (for inspiration, see the stuff made by Akoha) - 'gray water' counts as non-drinkable water allowances that can be traded for [X] minutes of showering (again, obviously we're on the honor system :P ), very rare 'potable' cards which can be turned into Gamemasters for [X] mL of water poured into their bottles. Other cards will be held by NPCs across Long Beach, which they will give you for completion of various tasks and puzzles.
Among the cards will be tasks, pieces of puzzles, and most importantly - components of a BioSand Filter which every team will race to assemble (once a team's BioSand Filter is complete, they are free to redeem all their remaining greywater shower-allowances tokens for 'potable,' effectively ending the game).
Part scavenger hunt, part fundraiser (we will set a portion of the participation fees as donation to Human Translation, an ambitious project to provide clean water to people in Cambodia), the Water ARG will be hopefully be a fun way to get to know your fellow BIL attendees while solving puzzles across the Long Beach area.
A number of things are already set - but I wanted to also get feedback since we won't have much time/manpower to playtest the game before it goes live.
Are you going to TED2009/BIL2009?
Would you be interested in participating in a 72-hour Water ARG as described above?
To cover costs in producing/hosting the game - we are considering charging $25/person to participate - with an optional 'donate [X]' to the water project in Cambodia. Does that sound fair?
Thoughts, feedback - please feel free to comment!