Revenue from the top 100 advertisers was down 18.3 percent compared to last year, data show.
Marketers that spend hundreds of millions of dollars in advertising join the protest starting today.
Also, activists rise up at companies, TV panel talks upfront reform and Retail Next is set.
Social network taps Media Rating Council to verify progress as more brands join protest to force oversight.
Site goes after communities it says were abusing its rules as it looks to become a safer place for brands.