Since 2023 more than 4,900 businesses have carried Yelp's "Consumer Alert" banner, which sits on a business's page for 90 days after it is caught planting or paying for reviews, according to a recently published working paper described by Eater.

Co-author Yi Cao, an assistant professor of accounting at George Mason University, says flagged restaurants' foot traffic fell about 8%, dipped further around the holidays, and most had not recovered to pre-alert levels even 18 months later. The team matched Yelp data with SafeGraph foot-traffic records and Consumer Edge card transactions.

Cao says Yelp relies substantially on reports from consumers and owners, plus an algorithm that screens for AI-generated language. "When the risk is relatively low, the business owners decide the incremental benefits are worth the risk," he told Eater.