The livelihood of the average paparazzo is threatened by major changes in the publication industry. The photographers manage idiosyncratic risk by forming unstable alliances, but the larger systematic risk that could wipe out their jobs is harder to manage. They could form a union and demand better terms from the agencies, but historically they struggle to cooperate with one another. And the paparazzi are not the only ones who face the risk that their jobs will no longer be viable.
Sounds like our discussions here in other threads when trying to figure out how to apply pressure for higher photographer income.