I'm new to this wiki, but I'd like to point out what appears to me as a deficience in GeoJSON. The properties shouldn't be treated as just additionnal attributes. I think that their type (number, text, date...) should appear in the stream, like it does for the type of geometry. In the case of a value list, it should embed all the possible values too. Why do I think these improvements are important ? Well, imagine we need to build some thematic cartography application, we must know how to deal with the fields to be able to apply the proper representation to them. When a value list can be displayed with unique values, a continuous number serie can be used to compute threshold and so on. It's not the same, and these approaches deeply concern geographic data.