There is a long back story behind this product. The wikipedia article[1] gets into some of it. For a while there was a chance that these stops would be required for all new table saws sold in the US. Sadly that time seems to have passed. The PTI (think MPAA for powertools) did an effective job of killing any regulations requiring the sawstop. Instead they have trumpeted these silly plastic guards as an effective alternative. I have yet to meet a contractor or hobbyist that has not removed the plastic guard from their table saw.