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It looks like Facebook (FB) is finally dabbling in off-site advertisements using Facebook targeted data, specifically for Zynga.com (ZNGA). This is likely just the first step -- as Facebook scales up, this could be a "Google Killer" move.
This approach is a little different from Google's AdSense network because it targets data already known about FB users rather than just keywords they've typed into Google or the type of content they've viewed. This could mean that you'll see specific ads related to products in industries you're interested in -- even if you haven't spent too much time online browsing that interest.
For people who spend a limited amount online, this could actually be a hugely beneficial trend, because ads will be super targeted even if there isn't an incredibly extensive browser or search history of their "interests". Either way, Google's monetization mostly comes from its ad network. Take out the ad network, and you've crippled them forever. This is because 96% of Google's revenue comes from advertisements.
Google is an online advertisement company that uses search engine technology to deliver those ads -- they make money through ads, not necessarily through search itself. This is why this is such an important development. Even if Google has the best search results possible, but Facebook begins undermining their advertisement network, Google will be greatly hurt.
If Facebook and Bing from Microsoft (MSFT) team up on an even stronger level, Google could begin a long trend downward. If Facebook brings out its own browser to compete with the Chrome, it could be even more deadly.
I've made it clear that I'm not rooting for Google, even though I think it'll most likely be fine in the short run. As I wrote in my last article on Google linked to above, Google has fundamentally changed its approach to how search rankings are done, emphasizing larger websites over smaller ones, even when smaller ones are equally or more relevant.
Overall, I think Google has lost the Google touch it had just three or four years ago. After decimating Yahoo (YHOO) for the most part, Google has changed its strategy, and now Facebook is in a position to deal some incredibly deadly blows over the next several years.