Keiretsu is a business term that defines a relationship between two businesses that is equally beneficial. This practice is often used between big businesses, such as corporations or manufacturers. This practice was developed in Japan after World War II. Banks encourage companies at the time to give each other deals on products and services to promote mutual success and, I am sure, improve the economy.
Michael Mann, the entrepreneur who bought seo.com for a newly acquired business, operates his entire investment fund after Keiretsu. He says that the purpose of this practice is to allow each small business that he has acquired to have reduced expenses.