Is Facebook treading on dangerous territory here? The ubiquitous social net is introducing a new ad format—Sponsored Stories—that turns the “likes” and other actions of their friends into promoted content. The ads–which will include the user’s name and profile photo–will appear on the pages of their Facebook friends in a strip on the right hand side of the newsfeed.

According to Mashable, advertisers can choose between four types of user actions to turn into a Sponsored Story: aside from “likes,” these include check-ins, actions within custom apps, and Page posts. For example, if a company has created an app, it can promote the actions users take inside them. Similarly, user postings to the walls of favourite brands can also be used.

Facebook has launched with some stellar partners, including Coke, Levi’s, Anheuser Busch and Playfish, and is to open up as a self-serve option in a few weeks.

As Mashable notes, Facebook is trying to do what Twitter has done: turn the content in their networks into ad dollars. The main difference between Promoted Tweets and Sponsored Stories, however, is that with Twitter’s Promoted Tweets, the advertiser still defines the content, while with Sponsored Stories its down to the user.

But with no opt out option, will users appreciate their actions being turned into ads?