A recent blog it posted came in response to a Wall Street Journal op-ed piece in which Nextag CEO Jeffrey Katz slammed the company and its practices.

that his comparison shopping site analyzes the search traffic it receives from Google and can tell "when Google makes changes to its algorithms that effectively punish its competitors," including his company.

"Our data, which we shared with the Senate Judiciary Committee on Sept. 21, 2011, shows without a doubt that Google has stacked the deck. And as a result, it has shifted from a true search site into a commerce site -- a commerce site whose search algorithm favors products and services from Google and those from companies able to spend the most on advertising," Katz wrote.

Google was quick to counter with a detailed blog to defend itself.

Senior VP of Engineering Amit Singhal wrote that Google's natural search results are never influenced by payment and that its "ads and commercial experiences are clearly labeled and distinct from the unpaid results, and we recently announced new improvements to labeling of shopping results."