There's a famous economics essay about the size of the firm by Ronald Coase (winners of the Nobel prize for economics), in which he discusses why firms (companies, organizations) exist at all (instead of individual contractors), and the factors influencing their size.

summary: http://en.wikipedia.org/wiki/The_Nature_of_the_Firm

actual essay: http://web.cenet.org.cn/upfile/30998.pdf