It's an explicit formulation of a process that you, and everyone else, follow all the time.

You might, for example, trust your spouse. You have no problem giving them your car keys, because you believe they are unlikely to steal the car.

Now a stranger asks you to borrow your car. You would probably not give them the keys.

But then you learn that the stranger is a good friend of your spouse. Because you trust your spouse, and they trust their friend, your trust in the stranger just grew, and you would probably consider giving them the car.

Using many such chains, with some discounting as the length increases, you could, for example, create a trust score for a news story.

In my opinion, this possible application would be rather counter productive as social trust at any scale is generally based on little more than marketing and public relations. Most would now say Harvey Weinstein is one of the most despicable people in this country - and his behavior was an open secret. Yet if you did any sort of networking trust mechanism just last year, he would have ranked near the top. And this is assuming we could perfectly measure such things. In reality that measurements, and measurers, are themselves rife with potential issues. And any measurement would be completely gamed.

Fundamentally, this would seem to do little more than work to entrench already established forces who would tend to the score the highest, or equivalently have the resources to the game the system most effectively.