Whatever do you suppose this is?
Zillow is a living, growing database of all homes — not just homes for sale (we currently have data on more than 80 million homes). More than 1.3 million owners have claimed their homes on Zillow and many have updated their home facts.
Kudos to Zillow for opening up their API’s. One can quibble with Zillow (for example, their neighborhood data, which appears to be… let’s say odd…) but the decision as a whole is brilliant.
Just add Offers of Compensation and what do you get?