The web is overflowing with implicitly structured data, spread over hundreds of thousands of sites, hidden deep behind search forms, or siloed in marketplaces, only accessible as HTML. Automatic extraction of structured data at the scale of thousands of websites has long proven elusive, despite its central role in the ?web of data?. Through an extensive evaluation spanning over 10000 web sites from multiple application domains, we show that automatic, yet accurate full-site extraction is no l...