 The online retail giant Amazon has reached a valuation in excess of $2 trillion for the first time. It's only the fifth company to do so. Amazon stock is up by more than a quarter since the start of this year. David Waddell has more details. Amazon joins an exclusive club. Just five companies, all American, all tech companies, are valued at $2 trillion or more. For all of them, investors are enthusiastic about how generative AI...