That's far from the only major lawsuit looming over Zillow. In late July, the real estate firm CoStar sued Zillow for copyright infringement and more than $1 billion in damages, claiming the search giant had cribbed some 46,000 CoStar-watermarked photos for use on its own website. Then, on Sept. 22, a pair of big-time plaintiffs' law firms — the same firms whose antitrust cases against the real estate industry resulted in a $418 million settlement and rewrote the rules around agent commissions — filed a class-action suit against Zillow. They accused the company of effectively driving up real estate costs by directing buyers to work with agents who pay Zillow as much as 40% of their commission from a deal.