> For the [Lean Startup] theory to be sound it must 
  > have predictive value

When did the Lean Startup method become the Guaranteed Startup Success method? My understanding is that Lean methods encourage startups to build short feedback loops to the things they're trying to accomplish: Capturing market, building the product, etc. The short feedback loops let the company know quickly whether their efforts are showing signs of success, and whether they should keep at it, or change their strategy. This is one of the points that Andressen is critical of, as well: Know when you're attacking a difficult problem and you won't get quick feedback.