Facebook CEO Mark Zuckerberg was called in front of the US legislators on Capitol Hill this week after it was discovered that millions of users' data was improperly obtained by a UK-based political consultancy group, Cambridge Analytica. They allegedly used that information to help target ads to support Donald Trump's presidential campaign and the Brexit referendum in the United Kingdom.
While Zuckerberg apologized and pledged to ensure such a data breach can never happen again, this scenario is a reflection of the ever-changing world of online advertising in which technologies help companies make money from processing users' personal data. There is a lack of transparency, trust and even insight into how this world operates.
Facebook puts out a lot of information on how to buy ads on its platform. The social network shows you how to create ads that don't look like ads, in what is known as native advertising.
Companies can then choose their audience based on demographics, location, interests and behavior. They can feed ads to other apps and mobile websites through the Facebook audience network.
All of this is completely unregulated.
According to GroupM data, by the end of 2017, Google and Facebook had an 84 percent share of global digital media - excluding China. Traditional media and ad agencies just can't compete.
Google and Facebook share none of the responsibility of traditional media and insist on being called technology companies - despite making more money from ads than every newspaper, magazine, and radio network in the world combined.
A "duopoly" has formed in the world's advertising industry, but even industry insiders admit they don't exactly know how it all works.
Frederike Kaltheuner, a data programme lead at Privacy International talks to Counting the Cost about Facebook, privacy, the secret world of online advertising, and regulation.
She says the conversation is about how "companies use personal data, and as it stands people cannot understand the way in which companies can exploit their data for advertisement."