Fireworks

Each year, we view some fantastic fireworks from the High School athletic field.  In addition to the fireworks, many people bring traditional sparklers (and sometimes other fireworks) that could easily burn and damage a synthetic field.  Sparklers burn at 2000 degrees (F), and can easily melt and damage synthetic turf.

Even FieldTurf's web site includes an article about how a town had to move their fireworks event to a different location, due to concerns about damaging the synthetic turf.

http://www.fieldturf.com/ru/artificial-turf/artificial-turf-news/mifflin-gets-first-of-synthetic-turf 

Vandalism

The possibility of vandalism, though hopefully unlikely, cannot be ignored.  I remember that there were a couple of times when someone intentionally damaged the school fields by driving a vehicle on it and doing "donuts".  Repairing a synthetic turf field is likely to not be cheap or as easy as reparing a natural grass turf field.