Hi! Welcome to the Insider Advertising daily for September 22. I'm Lauren Johnson, a senior advertising reporter at Business Insider. Subscribe here to get this newsletter in your inbox every weekday. Send me feedback or tips at ljohnson@businessinsider.com.Today's news: Walmart and Instacart chip away at Amazon's ad dominance, Quibi mulls a sale, and Suzy raises $34 million. Photo by Evelyn Hockstein/For The Washington Post via Getty Images Ad insiders say retailers like Walmart, CVS, and Instacart are starting to chip away at Amazon's advertising stronghold in the pandemicPatrick Coffee and Tanya Dua report that the pandemic has benefitted new e-commerce advertising platforms like CVS and Walmart.Amazon still rules e-commerce, but the pandemic marks the beginning of a long-term change that could threaten its dominance of digital retail advertising.Driving the trend will be small to mid-sized businesses like cell phone accessory maker BGZ Brands, which was able to quickly move ad dollars to Target and paid social when Amazon restricted the shipment of nonessential items early in the pandemic.Read the full story here. Jeffrey Katzenberg. Daniel Boczarski/Getty Images for Quibi Quibi is reportedly exploring strategic options including a possible saleThe Wall Street Journal reported Monday that Jeffrey Katzenberg's mobile-video startup, Quibi, which raised $1.75 billion but has struggled to sign up subscribers, is considering a possible sale.