For example, this post could have been a product of just probing a particular group of people to understand if they are interested in the subject and what they have to say about it.
That can be done indirectly, by suggesting someone (offering a link or planting an idea) that is already known to be interested in surveillance and prone to share interesting discoveries (in other words, the poster might not even be aware he could be an asset).
Think about the many ways someone could know your interests and how prone you are to react to something and how that could be used. If you are in tech, think about all the silly ways that kind of information can leak publicly.
People often disregard the possibility that they could be an active part of a surveillance network (as an unkowingly asset), instead focusing on more fantastical ideas such as technological hacks or coding wizardry.