Remember that "Lean" (SCRUM is really a subset of those practices) is at it's core a manufacturing process. Manufacturing isn't engineering. The author of the original post captured this very well:
> ...one can claim that this is not the job of Scrum, which is a software management methodology, and not a software engineering methodology, that it's only concerned with organizing the teams' time and workload
A manufacturing process can only drive quality if both the primitives and end system have gone through some sort of engineering process. Web developers love this stuff because they have components, frameworks and clients where the engineering details are taken care of in MANY scenarios.
Using a contrived scenario involving LEGO -- you cannot expect kids and parents to design new LEGO parts. The components are designed and engineered to work together in a completely different context. Carrying this further, if you want kids to assemble a consistent, specific artifact (Say a Star Wars X-Wing fighter), someone at LEGO needs to design that and produce documentation. Designing on the fly with sprints ("ok, kids, today figure out how to make a wing") isn't going to be a productive exercise.
Most SCRUM projects that I have personally seen fail are projects where "agile" is a codeword for "we didn't think this through, so we'll figure it out as we go". Then the "sprints" become a real joke as the team repeatedly runs into a wall.
