Google announced in late 2012 that Google Shopping would only publish products though paid advertisements in Spain.
The new algorithm called Google Merchant Quality, is responsible for the analysis of online stores based on customer feedback.
Although little is known of the new algorithm but it seems almost certain that Google Shopping will be the basis for the comments and ratings of products. Obviously, this algorithm will push companies be on Google Shopping. The only limitation may be reluctancy of most consumers value products in Google Shopping in countries such as in Spain.