The company appears to have begun promoting keywords in its "trending topics" list for sponsors.

When users click on a promoted trending topic, they are brought to a search results page, where the page is topped by a promoted Tweet. They aren't sent to an ad landing page, but to a live and uncensored conversation. That's what we're seeing with the new movie Toy Story 3 today at least. It's a logical and interesting way for the company to make money. It's also unlike almost any other advertising in history.