eBay and Amazon have feedback systems to help shoppers evaluate third-party sellers, and with the launch of its Checkout service, Google is introducing its own seller-rating system that is independent of marketplace.

"Reviews" allow buyers to describe their experience when paying for transactions through Google Checkout. Currently, only buyers and the merchants they rate can view the reviews, but in the future, Reviews will be available for public viewing, according to Google Checkout help files (http://digbig.com/4medd).

Buyers may post reviews after a transaction has been completed. Google Checkout Reviews feature two components: star ratings, a way for buyers to report on the overall experience; and comments, a way for buyers to describe the transaction, purchasing and delivery process in their own words. Sellers receive an overall rating score, which is the average number of stars awarded by all buyers who have posted ratings for them. Sellers who aren't happy with reviews are allowed to append comments beneath the buyer's review.

It isn't clear where Google will display a merchant's rating. A Google spokesperson said in an email late last week, "The reviews feature for Checkout is still being developed at this time, and we hope to have more information on it in the coming weeks."

As eBay and Amazon have learned, it's hard to please everyone when developing a feedback system. Last month, many Amazon sellers were angered when the company announced changes to its "Leave Feedback" page by adding three optional questions that buyers could answer about the transaction (http://www.auctionbytes.com/cab/abn/y06/m07/i10/s04).

Amazon's feedback page

A top concern among sellers with such a system is that buyers will use feedback as a replacement for communicating their concerns to sellers. Another major concern is that sellers will take the blame for delivery problems caused by carriers, not the seller.

When one seller recently received a survey from eBay on the topic of feedback changes, and it displayed an example of a new feedback system where buyers could rate sellers on specific aspects of a transaction, she wasn't happy. "I'm really underwhelmed by this one. While feedback system needs overhauling, being rated on the speed in which USPS delivers Media Mail doesn't thrill me." (Note that eBay often surveys members on possible changes, and features seen by survey recipients may not be implemented.)

A possible preview of eBay's future feedback?

eBay has viewed its feedback system as a key competitive advantage (many sellers have hundreds of thousands of feedback ratings) and prohibits its members from using their eBay feedback on other marketplaces or websites.

Two services have entered the feedback space with different approaches, Opinity and RapLeaf, but appear to be respecting eBay's "feedback turf." RapLeaf feedback, while portable, is not transaction-based, making it possible to game the system. Google Checkout's Review system has the same transaction-based advantage of eBay's feedback system.

Google's new portable rating system is also timely, as many sellers go "multi-channel." But its biggest challenge may be sites like eBay, which currently bans sellers from using Google Checkout.