When I was searching for a house I used 5 or so apps to do so. I found that Zillow had many, many listings that were very old, but were placed up top and the dates changed to make it look like it was just listed. However, checking the actual data for that listing shows that it was not pulled from the market and relisted, it was just Zillow constantly boosting really crappy houses that had been on the site for a long time.
In short, trust none of them, use multiple services, and keep looking constnatly. I found my house through my agents MLS system, which was about the time it showed up on the aggregates.
I was working with an agent and I told him I saw several houses I wanted to look at on Zillow. Sent him the list and all but one was sold. He said the listings were in some cases as much as 6 months old.
After that, he just plugged me into the MLS listings directly and then every time a new house would show up, I'd know about it and could email him if I wanted to see it or not.
I totally agree about not trusting 3rd party apps. MLS, unfortunately is the only reliable source I know of.
My area (Atlanta) is a very hot market. I found my house on Cinco de Mayo, emailed my agent, and we were looking at it that afternoon. By 9 AM the next morning the owners had accepted our offer. The house had not been on the market 24 hours. If I had not jumped on that house the moment it hit The MLS system, I would not be sitting in the backyard enjoying it right now. :-)
To amplify: I don't think it's any accident that the 2005 housing fiasco happened in this industry. Terrible pricing information (gaps + timeliness), as well as terrible conflicts of interest (buyers brokers are incentivitized to make the buyer pay as much as possible) make me wonder how much longer these dinosaurs are going to continue to operate the same way.
Do you mean the 2007-08 housing crash, or something else in 2005? If the 2008 one, it had a lot more to do with the financial side than the actual real-estate side, so changes in the real-estate sales process aren't likely to fix that problem. The "primary" dollar value involved in housing-price declines was significant but not really enough to cause an economy-destabilizing financial crisis. But the primary price declines in actual real-estate were multiplied many times over because the mortgages were all piled into heavily leveraged securities, priced based on risk models that turned out to be very inaccurate. That caused a crisis that ultimately involved dollar amounts greater than the total value of all the involved real estate.
A loose analogy: if you buy stock with 100:1 leverage, and the stock price declines 10%, you lose 1000% of your original investment. The big problem here wasn't really the 10% decline in stock values (significant but not catastrophic), rather the fact that you had 100:1 leveraged exposure.
In short, trust none of them, use multiple services, and keep looking constnatly. I found my house through my agents MLS system, which was about the time it showed up on the aggregates.