São Paulo felt odd to Dr Brent Coker when he visited, but he was surprised when he worked out why.
Outdoor advertising is illegal in the Brazilian city, so his brain – so conditioned to taking in marketing messages – had decided that the ad-free environment was unnatural.
For Dr Coker, who teaches Internet Marketing and Social Media at the University of Melbourne's Faculty of Business and Economics, it was yet another sign of how dominant advertising is in our lives.
We pick up our smartphones first thing each day, checking our emails, our Facebook feeds, and apps such as Zite.
In those few minutes, we are bombarded with advertisements, not all of them overt. Those disguised as "user content", such as the comment from a friend on a post by their yoga studio, which includes a photo of the space and a link to their website, also count.
Most of us accept advertising is part of life, whether on billboards, on TV, or our Instagram feeds.
And as the advertising space becomes increasingly cluttered, the challenge for marketers is finding a way to get their messages noticed amid the noise of everyone else's.
Indeed, on social media, it's no longer enough to just get noticed. Every marketer wants their content to go viral – to be circulated widely and rapidly across social networks. It's not easy to make that happen, as many marketers have discovered.
But according to Dr Coker, who covers the subject in his forthcoming book, Going Viral, there are some key reasons why some content will never be shared widely online. Keep reading.