Dave at Dispatches has another lovely analysis about the different kinds of startups taken from a book written by Amar Bhid�:

"It is common to view startups as being homogeneous. In his book, The Origin and Evolution of New Businesses, Amar Bhid� makes the case that business initiatives can be classified according to three parameters: initial investment, irreducible uncertainty, and likely profit. In turn, each class of initiative can be characterized by a set of initial conditions. Those typical endowments will provide us with some insight regarding the relative amount and kind of investment capital that is consequently available to each. The purpose of this section is to summarize some of the highlights of Bhid�'s framework. "