Twitter’s attempts at developing a viable business selling ads are in full swing. Twitter’s latest experiment in this area: paid trending topics.

As I write this, Twitter users will find ‘Toy Story 3‘ in the list of Twitter’s worldwide trending topics. But unlike the other trending topics, it has a prominent ‘Promoted‘ image next to it.

According to TechCrunch, Twitter has confirmed that Disney/Pixar are paying for the Toy Story 3 trending topic:

As we have always said, we plan to test different advertising and
promotional models in these early stages of our monetization efforts for both
user and brand value. As part of this effort, we are testing trends clearly
marked as “promoted” for an undefined period of time.

Like normal (read: unpaid) trending topics, clicking on the link generates a search result for the term. At the top of the list: a promoted tweet that Disney/Pixar is ostensibly also paying for. Below it: several ‘Top Tweets‘, which appear to be tweets that have been retweeted 100+ times.

On the surface, it looks like Twitter has come up with a fairly clever solution. The Toy Story 3 promoted trending topic is likely to expose far more Twitter users to Disney/Pixar’s promoted tweet, which has a link to Disney’s, a Facebook-based ticket sales application.

Of course, Twitter’s solution has to be more than just clever; it needs to deliver ROI. And when it comes to ROI, it’s not entirely clear that promoted trending topics, used in concert with promoted tweets, will ever be as effective as, say, AdWords when it comes to delivering intent and action. Two clicks are required (first on the trending topic, and then on the link in the promoted tweet). And since is on Facebook, Facebook members who aren’t logged in will have to log in. Non-Facebook members are, of course, out of luck.

Notwithstanding the structure of this campaign specifically, promoted trending topics also pose some risk for advertisers, as they can’t entirely control the tweets that appear in the search results. Not only could these tweets be negative, it seems like this may open the door for subversive guerilla marketing campaigns in some markets. Hypothetically, for instance, what would stop Reebok from engaging in a campaign to hijacking the search results for a Nike promoted trending topic?

Since promoted trending topics are an experiment, Twitter obviously has time to figure these sorts of things out. But one thing is clear: Twitter is serious about monetizing, and just about every part of the Twitter service is fair game.