How do you think this will effect companies like HouseValues, that get almost all of their revenue from lead generation for agents by enticing home sellers to inquire what their property value is and selling it to an agent?

This is the long awaited of often speculated about business started by Richard Barton, the founder of Expedia, the online travel giant.  Barton has raised over $32 million for Zillow to date.

Zillow’s business model is based on advertising, although I believe that will change to focus on lead generation along the lines of HouseValues and RealEstate.com once they reach critical mass.

The interface for Zillow is very easy to use, and real estate investors may find it of particular interest, allowing them to run quick comps to ballpark the value of a property before investigating further.