I have to say, some of the other teams' blogs really are helpful. Charlotte-Anne at the All-Knighters blog posted this tidbit from an interview with Jay Rosen about how Assignment Zero ended up working out.
Rosen: Your Wikipedia example is critically important. Here's why. I am on the Wikipedia advisory board, and in the spring I had coffee with Jimmy Wales when he was in town. I asked him why did Wikipedia work when the odds are that most things don't work, and he said something very important, although its significance escaped me at the time. People come to Wikipedia not knowing how it works, but they do know how a regular, 'ol encyclopedia works and so the "leap" to knowing what a free online encyclopedia would be like is not that great. This prior knowledge is critical to a system's viability because is constrains users and points them in the logical directions. How much did it cost Wikipedia to put that common understanding into each contributor's head? Zero! They already knew it. Explaining the way it works takes all of six words: "The online encyclopedia anyone can edit." With 6,000 words we did not get clarity on what a crowdsourced investigation asked of participants because there was no common image to start with, nothing comparable to "encyclopedia, right!..."
I think we pass the bar on part of the simplicity of explanation (even though we've been having problems explaining it). I think we just might be over thinking it. Essentially, it's consuming news and writing letters/emails. People understand both of those things, so the leap to directly tying them together shouldn't be too big.