Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Zillow (NASDAQ:ZG) rose more than 15% in Thursday's late trading following reports it is seeking to acquire fellow online real estate specialist, Trulia (UNKNOWN:TRLA.DL)

So what: According to Bloomberg, sources familiar with the situation say Zillow could place a value of as much as $2 billion on its smaller rival, and that a deal could be announced as soon as next week. To be sure, shares of Trulia also jumped by more than 30% on the news, giving it a market cap of almost exactly the reported acquisition price.

Now what: That's not to say such a deal is guaranteed to happen, but I can't blame the market for bidding up shares of Zillow today at the thought. To be sure, I touched on Zillow's sizable lead in the online real estate market only a few days ago -- Zillow grew its monthly unique users by 51% in its most recent quarter, to 70.7 million, compared to Trulia's still-respectable 42% growth to 44.6 million during the same period. Over the long term, if Zillow were to combine forces with its largest, fastest-growing rival this early in the game, there could be little to prevent it from absolutely dominating the industry going forward.

Steve Symington owns shares of Apple. The Motley Fool recommends Apple and Zillow. The Motley Fool owns shares of Apple and Zillow. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.