Why play-by-wiki and not play by email, or play on the yog-sothoth forums set up for the purpose? Basically, because this allows for a more dynamic form of world-building in which players can freely contribute, and a more natural style of interaction. Playing on forums tends to result in chopped-up and disjointed conversations, actions, etc, as posts inevitably occur out of in-game chronological order. A Wiki's dynamic editing makes the game transcript much clearer to all participants.
The Wiki format also enables players to make their own contributions to the game world, which I encourage. Although I will supply what in a tv series would be called the metaplot, I envisage much of the plot of individual "episodes" as stemming from PCs own actions and goals, which the Wiki format should help flesh out. This is also a simple matter of practicality. I will be spending about 1/2 an hour to an hour per day, no more, GMing this game, and so PC involvement is essential to maintain momentum.
The first appearance of something or someone significant in a scene should come with a wiki-link: e.g. each PC or NPC's entry should have a link to their page (if it exists).
Immediate threats will appear in bold text.
Out-of-character table-talk, game mechanics, comments, etc will appear in italics and should be prefaced by the player name. If you want to send a private message, do so through wikidot's message system.
Metagame disputed actions (e.g. if the Keeper describes something that violates something he said previously, or a PC does something that requires equipment he lost, etc) should be bulleted,
- like this
and once the issue is resolved will be deleted.
If you want to, in-game, alter someone else's action, you should use strikethrough text and describe what happens instead immediately afterwards. An initiative contest will usually be called for.
Eg: Bob draws his sidearm and shoots the cultist informant Jim grabs his arm before he can shoot. Bob and Jim then have an initiative contest to see who succeeds