Take a look at the complaint in Communications Workers of America v. T-Mobile US, Inc., et al., No. 17-cv-07232 (N.D. Cal.). It's a plaintiffs' class action naming a defendant class of hundreds of companies that have allegedly used recruitment ads on Facebook to target young people and thus discriminate against older potential job applicants. Here's the first paragraph of the complaint (edited to eliminate parentheticals and names):
The Communications Workers of America [and individual plaintiffs] seek to vindicate the rights of older workers to be free of age discrimination in employment advertising, recruitment, and hiring. They bring this action against T-Mobile US, Inc., Amazon.com, Inc., Cox Communications, Inc., Cox Media Group, LLC, and a Defendant Class of hundreds of major American employers and employment agencies that, upon information and belief, routinely exclude older workers from receiving their employment and recruiting ads on Facebook, and thus deny older workers job opportunities. These companies eliminate older workers from receiving job ads by specifically targeting their employment ads to younger workers via Facebook’s ad platform.
The complaint seeks relief under state anti-discrimination laws, but it promises to add claims under the federal Age Discrimination in Employment Act once the individual named plaintiffs have exhausted their administrative remedies under that law.