That first sentence gave me shivers because I know it's true. I don't think we realize the extent of the subtle but constant manipulation we'll all get to experience.
Usually brands pay for that screen time, but it’s not very obvious that it’s payed advertising.
The best advertising is word of mouth advertising and smart marketers seek out people of influence in their communities to spread their products. This was well known in marketing long before the term online influencer was a thing. It's very hard for most people to even notice this kind of advertisement is even happening.
- Do they actually own the product? - How long have they owned the product? - Show me how it works. - How much have you paid? Else it's worthless to me, but I'm happy for him/her
Product placement, especially without specific calls outs, are something subtle that most people don't notice. Something like the boxes of cereal sitting on the shelf in Seinfeld's kitchen. Are those ads, is it just set design? I don't really know.
There is also car choice in a movie or TV show. The studio isn't going to design and build an actual car just to avoid using a company's product. Which car do they pick and what does that communicate about the brand to the viewer. Is this an ad?