An investigation has commenced in the US into possible abuses of Facebook’s market dominance regarding data, advertising and consumer choice.

The leader of the investigation is New York Attorney General Letitia James, but she has got her contemporaries from Colorado, Florida, Iowa, Nebraska, North Carolina, Ohio, Tennessee, and the District of Columbia to muck in too. They all, apparently, are uneasy about the effect Facebook’s dominant market position has on all kinds of competition.

“Even the largest social media platform in the world must follow the law and respect consumers,” said James. “I am proud to be leading a bipartisan coalition of attorneys general in investigating whether Facebook has stifled competition and put users at risk. We will use every investigative tool at our disposal to determine whether Facebook’s actions may have endangered consumer data, reduced the quality of consumers’ choices, or increased the price of advertising.”

Yet to be announced by James, but widely reported nonetheless, is a parallel and similar investigation by the same AGs into Google. Of particular interest in both cases seems to be the digital advertising market, which is dominated in the US by the companies in question, as you can see from the chart below from eMarketer.

Since digital now accounts for the majority of ad spending it’s legitimate to be concerned about such a large market being dominated by so few players. Having said that it’s also reasonable to note that Google and Facebook have reached this position by competing in the open market and to the victor go the spoils. But however you achieve a dominant market position, once you do different rules apply to you and there’s plenty of precedent for such companies facing significant sanctions.