I wrote the first wiki in a week. Why has it taken me a year to write another? Short answer: when something is already surprisingly simple its hard to make it simpler.
This last year I set out to do for numbers what I had done for words, give them depth and meaning that ordinary people can depend on every day. A wiki, like a glossary, defines the terms we choose to use. A data-wiki makes those choices more complex. Its no longer one click to check a definition. Its more like one more study to check a dataset, to see if the data says what we think it does. Not a simple process.
My quest has been to make knowing and using data an everyday thing. This means the study of data must be an everyday thing too. To this end I've pushed visualization, I've pushed domain specific markups, I've pushed streaming measurements. But through this I've retained wiki's greatest strength: the ability to create with those who we have just met and don't yet have reason to trust. Finding trust on the modern web may be this year's biggest accomplishment.