Home values across the U.S. will drop by more than $1.7 trillion this year, 63% more than their 2009 decline, according to an analysis by real estate marketplace Zillow.com. It estimates that from a June 2006 market peak to the end of 2010, values will have fallen by $9 trillion. Zillow compiles its own "Zestimates" and includes all homes, not just those sold. The 2010 loss works out to an average of $18,108 per home. Zillow's data cover