On Monday a $3.5-billion deal was announced whereby Zillow is to buy Trulia with an aim to create a digital advertising juggernaut that could control more than 70% of online real estate searches.

Although this is breakaway from the usual trend of approaching the agents who had the monopoly on such market intelligence, still it is said that this could add on to the strain that is already causing an uneasy relationship between the sites and some agents and brokerages.

Zillow Inc. is Seattle-based and Trulia is San Francisco-based, both are offering a database in which search related to real estate data can be made. The users can view photos along with maps of recent neighborhood sales that too free of cost. This concept has helped companies to cut down on an annual price of $12 billion spent on real estate advertising.

Both Zillow Inc and Trulia operate by charging agents for home listings and for preferred placement on their sites, further, the sites invite customers to get in touch for more details on a particular property that they are interested in.

Real estate listing websites and their mobile apps has really picked up with users in the recent times thanks to the recovery in the housing market.

These sites have all refined up but still there is a lot of speculation that these sites charge more for advertising and also that the big brokerages respond by pulling listings off the third-party sites. Despite all this, both Billow and Tulia were able to serve 68.4 million unique users in June.

Mike Kelly of First Team Real Estate in Anaheim Hills said, "Before sites like Billow, buyers would come to our office and we'd tell them what was on the market. Now they call us and say they want to go see houses they found themselves".