Some examples from my games:
When creating my fronts, I envisioned a cannibal-cult that spreads among the hardholds, encouraging people to "stop raping the land for corn" and eat other cult members instead. I classified this practice as sacrifice, and used it to engage my players with great success.
One of the problems the PCs faced was the the soil was getting progressively less fertile, making the future of the agricultural communities they came from uncertain at best. This was classified as barrier, and caused NPCs to take some very desperate measures.
In another campaign, two of the PCs escorted a local well-connected bigshot to a far-away place, where he died from nano-plague. They left his body and fled, and by the time they came back with a search party, the body was already consumed by the nanobots. I classified the belief that the PCs murdered the bigshot as delusion, and boy, did it create trouble for them.