Mark Holan Staff Reporter- Washington Business Journal Email | Other Admit it, you're a Zillow-holic, addicted to checking online home value estimates. Every time you get near a computer keyboard you just gotta see the latest "Zestimate" of your own abode or some rooftop you're thinking of buying. Just type in an address, tap return and see what Zillow's algorithms say about the latest value of every house in the 'hood. David Howell has done this hundreds of times, but not because he's lost control. The executive vice president at Alexandria-based real estate firm McEnearney Associates wanted to compare Zillow's estimates against the actual sale price of residential real estates deals in Greater Washington. His analysis isn't encouraging. "Those predicted values are wildly inaccurate and inconsistent," Howell writes in a company report made available to me before being published in McEnearney's own newsletter, MarketWatch. Howell compared the Zestimates of 500 existing home sales (