One thought: this format works well if you have two axes (two APIs recombined into a new service/app), but what if you need three axes? Four? The remixing we'll see in the near future will recombine loads of APIs / data sources into single apps, interfaces and services. How do we represent a matrix more complex than 2?
What is the Web 2.0 Matrix?
Anyway, here is John's description of this new matrix.
"The Web 2.0 Mashup Matrix is now online here at ProgrammableWeb.
What is it? It’s an experimental interactive grid with Web 2.0 API’s along each axis and the intersecting cells correspond to the mashups made by combining each pair of APIs. As you move the cursor across the grid a box dynamically displays details about each intersection. You can go directly from the matrix to view the examples or drill-down into this site’s API database. The page is updated daily. You can get more details at the matrix’s About page."