oooo that would be sneaky!
Sorry, have now re-read and yes it seems that maybe there would only be 1 - therefore the highest bidder...... I thought it better to be the merchant plus one - therefore providing choice and options for the consumer to go either directly to the provider, or to go to an alternative that could be a comparison or review site.
If there was only 1 then - Google leave themselves open to the same lawsuit as is currently going on with regards to bidding against brand keywords - i.e. not every affiliate will be an affiliate of widget a for the term "widget a UK", some could be an affiliate of widget b company!
Are they seriously going to review every ad to make sure this does not happen - that would be millions of ads potentially?