Today it was announced that Zillow.com will be buying Trulia.com for $3.5 billion in a stock-for-stock transaction. Based on share of web visits, the biggest real estate website in the US has just acquired the 2nd biggest.

Both companies make the bulk of their money through advertising sales to real estate professionals (i.e. agents and brokers). But what was interesting to read in their press release is that, even with this merger, the combined revenue of both Zillow and Trulia still only represents about 4% of the estimated $12 billion that US real estate professionals spend on marketing each year. 

Zillow says it’s because the real estate industry hasn’t fully made the switch to online and mobile – and thus it represents a huge market opportunity for them. And from my experience I would say that this is likely the case. But it could also be because the real estate community is putting their marketing dollars elsewhere online. 

Whatever the case may be, Zillow.com (and its portfolio of companies) is now firmly positioned as the largest real estate website in the US. But even still, Zillow.com has never felt fully “