[mindcrime]

Knowing the product niche, pricing, market size, competitive advantage... all in the business plan ahead of time.

The whole point of the lean startup approach is to posit that the "business school approach" is wrong, exactly because you don't know all this stuff ahead of time, and that "business plans" are an outdated idea.

And if what you're doing is a truly novel product, then you almost certainly don't. If you're using the "fast follower" strategy to be the nth company doing a product in a certain space, then sure.

OTOH, even Steve Blank says that there are certain areas where you don't need to do Customer Discovery / Customer Development... like, if you're creating a cure for cancer, it's pretty much all engineering. If you build it (and it works) they will come. But I think that kind of scenario is the exception, not the rule.