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Google's selling radio ads. Print ads. TV ads. Billboards. But so far, it hasn't found a way to put its ads on Facebook. VentureBeat reports that Google is working on a AdSense program designed for the social network's corps of independent application developers. Don't look for complaints from Facebook — at least not out in the open. Facebook CEO Mark Zuckerberg's whole hope behind the platform was that third parties would find financial incentives to develop new features for the site. But the program raises a few awkward questions for both companies.

For one, Google is one of the parties negotiating with Facebook for a stake in the company and an advertising deal. If Google and Facebook come to terms, this program could prove a bit awkward, as advertisers find their ads doubled up on the page.

And then there's the question of how much cash Google ads will earn for developers. Google search ads work because they're matched to queries. Google's AdSense for content works on blogs because niche topics attract niche advertisers — fishing blogs will get ads for rods and reels, and so on. But what kind of context will Google draw on from user profiles to present relevant advertising? What kind of need does a user express by visiting a friend's profile? If anyone's going to figure out how to target ads on Facebook, it's Facebook itself — and sure enough, the company is quietly working on its own ad technology.