We added a personal request for this and the GOb2b developers suggested we add it as an idea here for potential future inclusion for all sites.
Google offers a service called Google Customer Reviews and in Google's own words:
"As a free-of-charge service, Google Customer Reviews allows you to collect valuable feedback from customers who've made a purchase on your site. On your checkout page, your customers can choose to take a survey to rate their experience with just one click. Ratings from customer surveys apply to store ratings."
This would of course be incredibly useful for building up a businesses presence on Google. It's not the most complex system to implement but it's also a little too complex to add for a single site. Hopefully others request this feature so we can all benefit from it.
More information can be found here:
https://support.google.com/merchants/answer/14628991?hl=en-GB
