One of Japan's biggest online retail sites, Yahoo Shopping, is under scrutiny for how it displays search results, with products from companies paying more in advertising fees often ranked higher in a practice critics say is "stealth marketing."
Two methods on the site that allow sellers to gain higher rankings have been called into question, according to industry experts.
In the first case, customers who search for goods on the site may draw an "item match" with a promoted product, lifting it to the top of the retrieval search results. Retailers also pay advertisement fees.