At Expedia (NASDAQ:EXPE), there’s more to travel than just online bookings.

The company's popular TripAdvisor website is taking a majority stake in FlipKey, a website that features user reviews on 50,000 vacation rental properties. One could even say that FlipKey is the TripAdvisor of stand-alone vacation homes, although that may not be fair to TripAdvisor, since FlipKey was launched just five months ago. It may also be an unfair comparison to sites like VRBO and HomeAway.com, which have been covering vacation rentals for years.

However, the move is indicative of Expedia looking to snuff out -- and cash in on -- a potential threat, by getting to it while it's still in its infancy.

Expedia is no stranger to acquiring travel-community sites. It has now snapped up a dozen niche websites like air-carrier seating configuration specialist SeatGuru.com and cruise-ship review hub CruiseCritic.com. Add up Expedia's collection of mostly Web 2.0-prolific sites, and its TripAdvisor Media Network attracts 24 million monthly visitors.

Expedia is in a league of its own. Rival booking engines like Orbitz Worldwide (NYSE:OWW) may encourage customer reviews, but they're no match for the 15 million reviews and opinions that TripAdvisor-branded sites have amassed over the years. In theory, staying close to so many travel buffs -- 6 million registered users and counting -- should give Expedia an advantage over sites like deal-seeker Priceline.com (NASDAQ:PCLN) and travel publisher Travelzoo (NASDAQ:TZOO). Expedia even owns a piece of China's eLong (NASDAQ:LONG), which isn't as exciting as snagging a piece of market leader Ctrip.com (NASDAQ:CTRP), but at least it's a great way to play a hot foreign market.

The rub, of course, is that communities are collectively smart. TripAdvisor doesn't hammer users over the head with Expedia propaganda, just as Amazon.com's (NASDAQ:AMZN) IMDB.com doesn't force film lovers to buy their DVDs through the leading movie site. However, it's always nice to know that the spigot is there if it ever comes to the hard sell.

So here's to Expedia and its globetrotting ways when it comes to snapping up travel websites big and small. If it's not the key to success, then it may as well be the FlipKey.  

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Longtime Fool contributor Rick Munarriz has been booking travel online since the 1990s, but he does not own shares in any of the companies in this story. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.