Most Internet users habour the mistaken notion that fake news and extremist sites have nothing to do with them. They do not visit such sites, and of course (ahem), they can spot fake and extremist sites a mile away.

Well, we all have to think again.

In mid-March, several major organisations pulled out ALL their advertisements from Google and YouTube targeted at the United Kingdom because their ads were appearing in extremist sites. The brands were responding to a March 17 report in the Times of London headlined " Taxpayers are funding extremism" observing how the algorithm of the platforms were displaying their advertisements on the extremist sites. Among the organisations: the UK Government, BBC, The Guardian, Havas, British Royal Mail, Domino's Pizza and Hyundai Kia.

As I write, Facebook too is rolling out initiatives to address the problem.

And the problem is this: advertising is the reason that many of the services we take for granted on the Internet are available for free or at minimal cost. If the advertising space is not trustworthy for advertising - that is, if the space is such that brands do not want to advertise-we could all literally be paying a higher price.

A theory that explains the importance of protecting the advertising space comes from Nobel-prize winning economist George Akerlof. His theory, which was the main reason for his Nobel, is that where there is asymmetry of information in a market, for example where one party knows what she is selling, but the other party does not know as much, the market eventually self-destructs.

The reason is that as buyers begin to lose trust in the information, the more trustworthy sellers begin to drop out of the market. After all, if people do not trust their information, they will look elsewhere to find buyers who will believe their information. As lower quality sellers remain, more buyers begin dropping out, until eventually, only the worst quality sellers are left and no buyers remain. At this point, the market has self-destructed.

It is no surprise therefore that Google and Facebook, which together command more than half of global online advertising by revenue, are taking action to prevent the self-destruction. The thrust of their actions is to deprive these extremist sites of the oxygen of advertising revenue. The same commercial logic can apply to fake news sites.

Their actions mean that both advertisers and advertising platforms are motivated to act. There is one more leg to the triangle: the audience-you and me. If the audience acts decisively to repudiate the advertisements - e.g., by declaring that they will boycott companies that advertise on fake news and extremist sites - the incentive to create such sites will be choked off.

We can play our part by alerting the advertisers and the platforms. It is crowdsourcing and community building in action, calling out the best from us.

No, we will not eliminate all advertising from fake news or extremist sites. We make it a lot harder for them to use the Internet against us.

If we do that, we will be making our little corner of the world just that little bit brighter.

Peng Hwa Ang is a founding member of the ISOC Singapore Chapter. He is a professor at Nanyang Technological University and was a member of the Working Group on Internet Governance. The views and opinions expressed in this article are those of the author and do not reflect the views of the Internet Society.

More photos from the events