A new campaign challenges Facebook users to spend 99 days off the world's biggest social network.

Intended to be a response to Facebook's recent "mood experiment," the "99 Days of Freedom" initiative launched earlier this week but so far has only brought in 2,600 users, ABC's Good Morning America reported.

Just, a creative agency based in the Netherlands, started the campaign following the revelation that Facebook experimented with the moods of 700,000 users.

"Facebook is an incredible platform, we're all fiercely loyal users and we believe that there's a lot to love about the service," Merijn Straathof, the art director at Just, said in a statement. "But we also feel that there are obvious emotional benefits to moderation."

"Our prediction is that the experiment will yield a lot of positive personal experiences and, 99 days from now, we'll know whether that theory has legs," he added.

Facebook data shows that the site's 1.2 billion users are on the social network for an average of 17 minutes per day, which would add up to more than 28 hours in a 99-day period, said a Just press release.

In a 2012 social experiment, Facebook toyed with the emotions of 700,000 users by putting more sad news in some feeds and more happy news in other feeds, the AFP reported. The results of the study were published last month and resulted in a backlash from users since the site didn't obtain permission before conducting the research.

As for the 99 days experiment, some participants were off to a rough start while others enjoyed having the extra time, Straathof said.

"Day 1 is the roughest. I am always looking for my app when I deleted it. I feel empowered to keep doing this though. I know I can stay strong!" wrote a user named Henderson Cunningham, as quoted by Good Morning America.

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