What was the name of the house valuation site... Zillions or something

Powers said his board members have had mixed results on tests they've been running since Zillow's public beta test went live. "In some areas, we found the results were fairly accurate to the value of the home. In others, we found results that were at least 40 percent wrong."

Zillow president and co-founder Lloyd Frink said the free, advertising-supported site doesn't aim to replace home appraisers or real estate agents. "It is meant as something to help buyers and sellers start a conversation."

How does Zillow work? It starts by buying massive amounts of real estate information from commercial data collectors -- home addresses, tax assessments, square footage, lot sizes, number of bedrooms, prior sales prices and the like. Then its computers identify similar homes that recently sold in the same neighborhoods and use mathematical models to compare their traits and create a "Zestimate," or "estimated market value."