This made me think of something Peter Drucker wrote, and I think it came from the article summarized here:
http://knowledgeworks.wordpress.com/2007/06/05/article-the-c...
pg says that the modern firm is the product of modern technology, but this summary of Drucker's article points out that technology is also obviating the need for much of the "middle management" layers that pg criticizes as anathema to humankind's natural state.
I'm pretty sure somewhere Drucker also says that the only reason to keep activities within a single firm is because the transaction costs are lower than having activities performed by an outside firm. I think he also argued that as transaction costs between firms fall due to technology, it makes sense to "outsource" more and more, which of course we are seeing in today's economy. Which suggests that we should see more small firms over time.
Too bad Drucker is no longer with us. I'm sure he would have a lot more interesting things to say relevant to startups.