Research firm Forrester reported that 30 percent of U.S. online shoppers in the third quarter began researching their purchase on, compared with 13 percent who started on a search engine such as Google – a reversal from two years earlier when search engines were more popular starting points.

Search ads work so well thanks to purchasing intent. Retail shopping isn’t the only game, but it’s an important one. This isn’t good news for Google.

I agree with the larger analysis here. Whereas the past couple of years have been all about “Apple vs. Google”, I think that shifts to be more about “Amazon vs. Google” in 2013. The two increasingly have more overlap when it comes to each of their key businesses.