The engine that runs Google is advertising. So what do you do if you're Google and you want to make more out of your ads? Put more ads in them.
Google is flagging improvements for retailers utilising Google AdWords due to be delivered to its mobile Adwords product. It's trialling a scheme it's calling "Buy On Google", which will see ads adorned with an additional Buy On Google text link. That link would lead to a retailer-branded page, but one hosted by Google itself, finally using Google Account itself to pay for the purchase.
Which means at this stage that this is a US-only initiative — but Google being Google, when there's ad money to be made, or for that matter a cut of retail sales, it wouldn't be surprising to see it shift globally relatively quickly.
Winning the shopping micro-moments [Inside AdWords]