ChatGPT is testing ads for some U.S. users on both the free and Go subscription tiers, its most affordable offerings. Why it matters: It could be the beginning of the end of ad-free ChatGPT.What they're saying: "Our goal is for ads to support broader access to more powerful ChatGPT features while maintaining the trust people place in ChatGPT for important and personal tasks," an OpenAI spokesperson told Axios. The company says ads will not influence ChatGPT's answers, which it says will remain...