You may have seen seller rating extensions like these in some Google AdWords sponsored links lately. Note they are a little different depending on whether they show in the top of the page sponsored links or on the right.
This is the newest ad extension available to AdWords advertisers. If an online store is rated in Google Product Search, with 4 or more stars and at least 30 reviews, seller ratings can be associated with its AdWords ads. These ratings will show up automatically if the above requirements are met and there is no set up involved.
As of now this feature is in limited release but is being rolled out to all eligible accounts.