When I blogged about App Inventor for Android a couple of days ago, I focused on the fact that it's closed source. What I didn't say, but should have, is that I think drag-and-drop programming tools are an idea whose time should have come at least twenty years ago. Tools like QuickFuse (for building voice response apps) respect the 80/20 rule in a way that even the simplest "real" programming languages don't. Like SQL, they're a good solution to a single, but important, sub-problem.
So why are tools like Scratch stuck in the playground? Why doesn't my PVR come with a drag-and-drop programming system? Why doesn't OpenOffice, so that people can automate simple repetitive tasks? Why haven't any of the dozens of such systems that have been built to manage scientific workflows over the past 25 (!) years ever caught on? Will App Inventor do for drag-and-drop programming what the Mac did for windows and mice, or the World Cup did for the vuvuzela?