One online ad trend in social media is to use people’s digital responses–their likes, their comments, even their photos–in an online ad. Many people, though, do not appreciate their inadvertentl starring role in a company's ad.

The most recent illustration of this comes via Facebook, which is being sued in a California court for violating a state law regulating commercial endorsements. U.S. District Judge Lucy Koh in San Jose rejected Facebook’s bid to dismiss the lawsuit , Bloomberg reports.

He ruled that the plaintiffs may pursue claims that the company's sponsored ads are fraudulent. Facebook's ad format, the sponsored story, has gone live on the site's homepage ticker after toying with test versions throughout the last two months.

Facebook launched the sponsored story format with seven different variations, but as All Facebook points out, the format that tells viewers that their friends like a particular brand or page seems to be the most popular.

The LinkedIn Fiasco

Earlier this year, LinkedIn tried to launch a similar ad format, but its users revolted. The site introduced in-house ads that used members' photos, but confronted with a backlash, it retreated.

Post with a Link

Interestingly, the most-cost effective exposure a brand can get on Facebook is a comment on a post that contains link.  This results in almost 5 times the amount of clicks of that link than a like of a comparable post, according to EdgeRank Checker.

Data from the analysis indicates that for every like a post gets, its link receives on average 3.1 clicks. Meanwhile, for every comment a post gets, it receives on average 14.7 clicks. Overall clicks per impression were found to be 0.005.