It's not impossible for a big viral challenge to contribute something positive to the world, but it's often the case that the popular ones tend to be pointless, yet harmless at best and actually harmful at worse.
After all, for every ice bucket challenge intended to raise money for ALS research, there were several stunts that had people do distressing things like eat laundry pods or set themselves on fire.
Fortunately, the #trashtag challenge is a nice return to positive form after a couple of years of madness.