Knowing that a snapshot of a Facebook post taken out of context can land that person in jail for months is a goldmine opportunity for some people.
This just adds to the list the other things could include: plant child porn on their machine, call the terrorist hotline with a tip, launch a flood of ssh port scans into a .mil address from their machine, and bam! easy peasy that person's life is ruined.
This is not unlike the witch hunts in repressive regimes where people are encouraged to rat on each other. Quite often that is taken advantage. It used to be report the person to be a "Communist" or "report that person to be an Anti-Communist".
Unless there is public and swift punishment for the prosecutors or the "professionals" in the chain of people this has passed through, this will repeat again and again. There is just very little incentive not to "keep going" with these tips. The potential repercussions for ignoring it could be much harsher. So why not...