For the past two weeks, I've been conducting an experimental blog-based game - Super Random Adventure Quest!
So far, it's been a blast, an excellent exercise in creative writing, and an interesting way to stay in contact with Huntsville. I keep wanting to pull down the screen and ask how they're liking it, but judging by the somewhat regular attendance, it must be a least a little fun.
I fear treading the line between too random and too boring. If there doesn't seem to be any plot, and if the player's don't feel they have any control, unless the random stories are just a cracker-jack read, interest will be lost. Or, if things get too hum-drum and each post gets too predictable, interest will be lost. Basically, the players need to be allowed to drive the story, but when you reach unexplored territory be ready to fill it with something different.
As far as planning, I've got an overall idea for the game, and as far as the next few rooms, I know what I'd like to see, but I don't have anything set-in-stone, and I definitely don't have anything written ahead. Planning is sorta important for two reasons. One I mentioned above - the need for a sense of plot, but the other is to avoid arbitrarily screwing over the players. I could just have the next door they forget to search be the one with a deadly trap, but it's better to know that when the room is revealed. It lowers your guilt when something bad happens and creates genuine success when the team artfully dodges a sticky situation.
Ultimately, I plan on keeping this going for as long as possible, as long as I have interested players, and if we happen upon some sort of ending... I'll figure that out when we get there.