It really depends.
I don't think anyone would move just yet unless it got to some insanely large number of people being killed.
But I'm sure no one chose to move the the Washington D.C. area (well at least w/o any doubts and insecurity) just because they wanted to, during the sniper atttacks. So yes, others do influence your decisions.... is it worth moving over... depends how much you like that place, job situation, family, etc.
Im sure if there was a sniper in your home area and you hated the place already and were able to get a job at another location, a lot more people would be moving.