Good job. I had to wonder about your description of Scratch as "once users have posted their content on the site they receive little feedback from other users". It seemed to me that there many projects within Scratch where people collaborated, sometimes even independent of each other, where someone created graphics, someone else created an animation out of the graphics, and others again program a game around these animations. While there might not be much direct feedback (don't have any stats on that), there is the possibility of, and support for, remixing which you unfortunately don't mention at all. How does remixing influence/interact with meta-design?