A piece of content that changes everything. A new idea so revolutionary that changes the worldview on some topic for a large group of people. A revelation or "leak" that has second and third order effects on the world. Or something simple. A blog post that actually gets you over 1000+ visits and a shoutout in NYTimes. It can go bad as well. A piece of content that stirs up a controversy leading to multiple lawsuits.
The coming years we will see more of this. The nature and scale of the internet will make this phenomenon frequent but still rare. It will be harder to spot from all the clickbait content out there. However it will be very clear to point out in hindsight which piece of content changed the course of our collective thinking.