Trulia-Zillow Deal Doesn't Build a Moat for Online Real Estate

Trulia's public debut, in 2012, was capped off by a big run throughout a bull market and a $3.5 billion dollar sale to its biggest competitor, paving the way for the merged unit with Zillow to turn into a titan in the online real estate space. However, competitors are emerging, like 42Floors and Open Home Pro, looking to carve niches into Zillow/Trulia's highly lucrative business. More M&A could be on the way, as well, as these two companies look to defend their high ground. They could take a page from LinkedIn, which has spent a fortune on M&A to start the year -- this, after a conservative stance.