Interest check-wise; I want to get an impression within the first few seconds. Before I have an idea of what your game is about and what I'm going to do in it, everything is fluff. You might write down a king's letter, but unless it begins like "Dear adventurer, I need you and your magic powers to recover my kidnapped daughter from the clutches of the evil kingdom" I'm going to scroll through your post until I can summarise the premise in a single line and know what options are available to me as a player. In fact this is exactly why, in Ergo's example, I'd actually put the picture below the italics. It's not relevant until then; rather it is in my way (although other than that the example is fine.)

The main problem with interest checks as a format itself is that beyond saying "Hi, I'm interested." It doesn't allow for much interactivity, so it's smart to give players some tools or bricks to start building their characters with, or leave descriptions a little vague and compelling to ask for more detail (fine balance, it's tricky.) Interact with the potentially interested, prompt them to do something early on besides waiting, because it'll increase their involvement and therefore commitment.

[quote=Brovo] Why? I have no idea. Go ask a psychologist.
[/quote]

Emotional impact, mostly. People are more likely to listen when you talk directly to them than to a big crowd. Successful communication to audiences in fact, relies on either making every individual able to connect to something in your speech, or making the crowd one big organism they're swept up in. Successful storytelling relies on emotion and immersion, something a wiki structure doesn't give you.