Over the last decade, the Internet has seeped into that bedrock of the U.S. economy: the housing market. A group of growing and mostly profitable websites like Redfin, Zillow, Trulia and Realtor.com have sprung up to help guide consumers through what in many cases will be the largest and most nerve-wracking transaction of their lives. But by and large these companies are not dislocating real estate agents themselves. A majority of buyers and sellers still wind up working with traditional brokers, one on each side of the deal. Here’s the full feature story on Businessweek.com, about the lack of change in the real estate business and how three of these companies have a surprisingly intertwined past.