Facebook hasn't found an ad model that works, but the social network is hoping that it's new Engagement Ads program may deliver the goods.

Forrester Research analyst Jeremiah Owyang first wrote about the new program on his blog.

In a nutshell, the ads come in three flavors, but unlike banner ads, they are designed to work inside a user's Facebook profile, rather than taking them away to a branded microsite.

"Facebook is conducting a trial of Engagement Ads over the next few months as part of its continual development of additional advertising concepts," a statement from the company read. "The initial three versions of Engagement Ads will allow users to make a comment, give a virtual gift or become a fan of a brand's Facebook page directly within the ad. People also can view recent friends who made comments, gave a gift or became a fan both within the ad and as those actions are shared through News Feed."

Facebook, which recently got a boost from Fox News' decision to use the social network over rival MySpace, has had a hard time getting most advertisers on board. Many advertisers remain unconvinced that Facebook users are interested in their ads (perhaps a reason for the dismal clickthrough rates on banners). At the same time, Facebook hasn't entirely put the Beacon fiasco behind it. Last week, news broke that Facebook and several of its leading advertisers had been named in a lawsuit for allegedly violating the privacy of their users.