When I first saw the headline “Facebook Places Ads on Zynga” on The Wall Street Journal, my mind almost fell into an infinite loop. You see, Zynga is already buying ads on Facebook to promote their games. I had thought that headline meant that Facebook is returning the favor by buying ads on Zynga to bring on more users.

Nope.Turns out Facebook is testing out their own ad network on Zynga. Yes, looks like Facebook will be launching an ad network to compete with Google’s Adsense.

I thought it curious they would test it on another social network, where click-through rates tend to underperform. They would probably get better results to show their advertisers on a content site like The New York Times, for example, where ads have a much better performance.

The bottom line for a site owner is revenue. If I can make more from Facebook Ads than Adsense, then I would switch. Click-through rates for ads might be crappy on Facebook, but on other sites, they might be better, especially if they’re highly targeted.

Ads from Adsense have high relevance, but Facebook Ads are more targeted. Will better targeting beat relevancy? We shall see.