Honestly, if we looked at every existing course in the directory and checked them for safety concerns similar to the one that precipitated the Polliwog incident, I'd say a scary portion of them would have to be considered for removal, and many more yet would have to be drastically altered to make them reasonably safe.
That being said, with all of these such courses in existence, I'm surprised that we don't have more incidents than we do. Yeah, all it takes is one, but perhaps the fact that we don't see that one very often is testament that we're a bit more considerate about sharing the parks with other users than we would think.