Groups like Snapchat, Twitter, Amazon, Foursquare, LinkedIn and Pinterest were called out in a new Association of National Advertisers (ANA) report for not agreeing to third party measurement audits by the Media Rating Council. The Media Rating Council essentially acts as the media and advertising watchdog, and their audits of advertising metrics are considered the industry standard.

ANA claims the companies are "walled gardens" that restrict convenient access to vendors they don't approve that could independently verify the validity of their metrics. As a result, some of these companies could get away with reporting false advertising metrics, as Facebook and Twitter did in 2016. (Both companies later owned up to the false reporting.) Google and Facebook both and agreed to MRC audits earlier this year.

Why it matters: Ad buyer confidence falters without transparent metrics. For example, ad agencies and vendors said they and their clients were wary of buying Snap ads earlier this year, because they don't trust the metrics the company reports back to them. As a result, Snap has added more third-party measurement vendors to its roster, but ANA executives and industry professionals say an audit would ease concerns.