Real estate Web site Zillow.com just announced it broke multiple records for site traffic and user activity in 2009, with 8.2 million unique users for the year. This represented a 57 percent increase over 2008 traffic. Additionally, page views increased 37 percent, and the Zillow IPhone app, which Zillow has described as “the most popular real estate app on the IPhone” was downloaded 870,000 times in 2009.

Many Zillow changes, as reported by AIM Group, may have helped lead Zillow to these impressive numbers and the company’s mobile-app O’Reilly Media title of “Best App for Real Estate.”

We reported, for example, the recent launch of Zillow rental listings and search, and a new collaboration with Redfin for the Zillow Mortgage Marketplace. As of 2009 year end 550,000 loan requests have been submitted to the Mortgage Marketplace, resulting in 10 million custom loan quotes. More than 250,000, (46 percent) of the total loan requests were for refinancing as mortgage rates fell to record lows.

“2009 was a wild year for real estate, with continued home value declines, government intervention, record low mortgage rates, and an enormous amount of consumer uncertainty about what the future holds,” said Spencer Rascoff, Zillow’s chief operating officer, in the announcement. “As a result, people flocked to Zillow for information and advice. Uncertainty always benefits information providers, and 2009 was the year that Zillow solidified its place as a clear leader in providing millions of people with real estate information.”

AIM Group has also pondered how the pending bankruptcy of Zillow marketing partner Foreclosure.com might affect Zillow. Here and here are more on that discussion, including Zillow’s comments.

In 2009, 171 newspapers signed up to use the Zillow API. We wrote about one of the latest, Boston.com, the online home of The Boston Globe. Read here about its customization of the Zillow product.