I'm less worried about cases like the Mont du Chat descent, more concerned about incidents like the Peter Stetina crash at the Vuelta a Pais Vasco a couple of years ago, which was the result of failures by race organisers to remove road furniture or provide adequate warning of its presence, or at the very least protection against impact.
Richie Porte's crash was of his own making. I feel sorry for him, and I'm glad it wasn't worse, but I'm far from convinced that he is justified in blaming the course design.
I've heard it said that the problem is down to the fact that riders these days are racing down the descents, whereas in the past the descents were effectively neutralised. This is patent nonsense - as far back as 1974, it was Merckx pushing too hard on a descent that caused the crash that put Ocaña out of the race.
Then there's the famous Wim van Est ravine incident in 1951, which happened after he had lost time on the climb and was pushing hard on the descent to catch the race leaders.