Yesterday the blog Facebook Insider reported that TripAdvisor acquired Where I've Been, the top travel-related application on Facebook. While TripAdvisor later denied the rumor, the ensuing story exposed something: The exploding number of applications on Facebook. Thanks to its Facebook API program, Facebook is fast becoming the front page for much of the Web.Last month, I argued that Facebook posed a challenge to professional networking site LinkedIn. While I stand by that assessment, I think that in that post I didn't go far enough. Given just how fast Facebook's API program is growing, Facebook may present an even more interesting challenge to the Web. Facebook could shape up as a rival to Google, Yahoo, and even search itself.

By integrating more applications into its platform, Facebook is trying to transform itself from being just a social networking platform to becoming a full-interactive control panel or remote control for the Web. Unlike earlier attempts to do this -- think of the portal model of Web 1.0 -- Facebook has designed its API system so that users can access all the Web sites they want without ever leaving Facebook, or opening new Web pages. I suspect that Facebook will expand this functionality so that eventually the entire Web can be accessed through these widgets.

In short, Facebook wants to become the locus of control for much of the user's Web activity, letting the user seamlessly share travel information, pull in news updates from blogs like TechCrunch, or send questions to the user's social network with apps like MyQuestions.

If you will allow me to extend the remote control metaphor, Facebook users no longer have to go "out there" in the rest of the Web to get new sites, they can pull them through Facebook, either with invites from the app providers or, more effectively, through their social network itself. The cumulative impact of this could be huge. Just as the remote control gave birth to the couch potato (the ultimate passive TV viewer), so too could Facebook change the game for Web use.

If users no longer need to search to find new cool Web applications, they won't need to use Google, Yahoo, or MSN as much. Instead, they can rely on Facebook for finding new applications. Now, I don't think this would mean the end of search, but it could reduce its importance pretty significantly. If that happens, Google loses power and Facebook gains it.

What do you think? Do Facebook and its exploding universe of applications pose a real threat to Google and search in general?