[JesseK]

It would seem that defensively bumping a trackball backwards after it's been hurdled would earn a much larger point differential than simply pinning a ball in place. It allows you to keep moving and forces the opponents to do 2 laps before hurdling that ball again (20-30 seconds of delay) instead of sitting in place for 15-20 seconds. Of course, this is subjective to being in the right place at the right time.