It appears that Google accidentally let loose a glimpse of a forthcoming product called Google Trusted Stores today. There is a landing page and a video, but you can't see either one right now, unfortunately.
Spotted by Alex Chitu at Google Operating System Blog, there was a video uploaded, which was at one point viewable, but has since been made private, talking about the product, which would be found at google.com/trustedstores, though you only get an error message if you go there now. Here's an image of the video, which is now unplayable in public.
Chitu quotes the video as saying that the program "makes it easy for online shoppers to identify stores that provide an excellent online shopping experience." Chitu says, "It's likely that Google will show a Trusted Store badge next to the ads for the online stores that provide a great experience and have a good track record of shipping on time and providing excellent customer service."
This wouldn't be the only thing Google is doing to establish trust in its search results, whether they're organic or paid results. Google+, which Google considers to be largely about identity, is a major factor at establishing trust.
Google's +1 button, which appears not only on organic results and web content, but on paid results, will likely be a major factor in establishing trust as well. As discussed here, it will likely be not only about how many +1s, but who is doing the +1ing.
As far as building trust for your store using the +1 button, you want to note that Google recently announced a couple of e-commerce platform partnerships around the button.
Google says it doesn't have anything to announce in relation to Trusted Stores right now, but I'd imagine we'll see an announcement soon.