Inside Google's fierce Goliath-versus-Goliath fight against Amazon for shopping dollars

"When I first started out in advertising and engaging with these partners, Facebook knew what you liked, Google knew what you searched, and Amazon knew what you bought. Those things became interconnected but blurred at the same time."

"A survey carried out by Morgan Stanley in March this year found that 61% of US consumers said they visited Google sites first when researching a product online, up from 57% in November."

"It's fine to let the machine make all the decisions because they can do it at a much higher frequency and much more often to get the best possible results, but at the moment I don't have enough visibility into all the signals and where to spend my time improving which signals get the best-possible performance."

"But Davis and other ad experts said the drive for simplicity sometimes came at the expense of the needs of more sophisticated e-commerce advertisers. They want more bells and whistles to enable them to increase a shopper's average basket size or to optimize their targeting around their highest-margin products."

The quest to be shoppers' No. 1 destination has two tech giants pitted against each other. After losing ground to Amazon, Google is doubling down on Shopping to be customers' first choice.