Amazon’s ad business is booming. Some advertisers are moving more than half of the budget they normally spend with Google search to Amazon ads instead, amounting to hundreds of millions of dollars, according to execs at multiple media agencies. Some of these execs requested anonymity as they are not authorized to discuss their clients’ expenditures in public. Amazon’s growing success could pose a rare threat to Google parent company Alphabet, which generated $95.4 billion in ad revenues last year, 86 percent of its total revenue. Google is the dominant digital advertising platform in the U.S., and will take in an estimated 37 percent of digital ad budgets in 2018. Although Alphabet does not disclose the breakdown of its ad revenue, most estimates believe the vast majority comes from search ads — approximately 83 percent in the year to date, according to research from eMarketer. Read more at CNBC.