The idea of a lean startup is attractive in that it is an effort to make the startup process capital efficient, getting the most bang out of the startup dollar and doing early testing to make sure that assumptions  hold up under the test of running them by  potential customers before investing a lot of time and effort in building out products based on those assumptions.

The movement seems quite new and possibly a bit faddish but it has its roots in the Toyota way of manufacturing transformed into a method for creating startups. This is a much longer pedigree and a great deal more reassuring.