I once witnessed a near stampede created by two businessmen in shirts and ties who were calmly jogging down the sidewalk in downtown San Francisco.
This guy who saw them froze with fear, looking behind the joggers for the threat, because why else would someone in normal clothes be running? He ran right up to them and then past them because he knew that the pitbull/bear/murderer gets the slow guy. Other people on the sidewalk saw this, and in moments, a chain reaction occurred and there were dozens of panicked people running down the street, some screaming, frantically looking over their shoulders for the culmination of every bad dream they've ever had in their lives. Each new person who saw the group thought "I don't know what they're running from, but I'm not willing to find out" and joined the group.
So really, you should never do it. It's irresponsible.