Sorry for not posting in a long while. I've had a bit of a pox on my house, shall we say.
Infocult had a really interesting post a while back on antecedents to alternate reality games. It's an interesting post in its own right and because of the questions it asks, and better, Bryan is in the habit of updating it periodically as new ancestors catch his attention.
One of the big questions on my mind lately is from whence the designers of ARGs should pull our best-practices. We need a theoretical framework around which to build our creations, and nothing seems quite a perfect fit. So it's instructional to look at that list of proto-ARGs and see that none of them really provides the sense of structure I'm looking for. And the sense I have more and more is that it depends on what component of a game you're talking about.
For recorded events, live events, phone or chat interactions, we probably need to borrow from theater and develop a discipline of rehearsals and notes. (Ah, but is it too much work for what is often a one-night show?)
For written works, the literary world has a well-documented practice of draft and revision. The question here is when is enough. (And are revisions on a two-sentence blog post strictly necessary?)
For puzzles and web games, we can borrow the traditional game design practice of iterative design, or put more plainly, play with the game until it is fun and works the way you want. (Though it can be a trick to find discreet play-testers under an ARG's signature veil of secrecy.)
These are easy enough answers, but then how do you pull it together? I think it could be informative to investigate the writing practices of arc-style TV series to see how pacing and continuity are handled in a similarly collaborative environment. There will always remain, though, the difficulty of interactivity. Imagine if your favorite TV series were always a live improv performance, with much of the substance generated on the fly but still needing to all hang together neatly, and I think you come close to imagining the basic challenge a puppetmaster wrestles with. Every night is opening night.