There's always someone who wants to do the craziest things.

Some people seem to think that the National Parks and the sights there in are Disneyland.
What makes these places still somewhat wild and beautiful, also makes them places to be careful and respect the power of Mother Nature. Buffalo, wolves, elk, bears, and other large mammals are not domestic pets. Waterfalls, rivers, lakes, cliffs, are not Mr. Toad's Wild Ride.
I would hate to be denied access, or have huge fences erected in the national parks because of a few not very prudent people.

One person is critically injured, and three people are dead. As tempting as it is to be publicly critical, maybe we're better off just having our thoughts be with their families during this devastating time.

I remember years ago being in Yellowstone at the lower falls with my family. Some guy did the same thing...climbed over the barrier, slipped and went over the falls. I remember my mom covering my eyes.

For a less somber, but still Darwinian note, consider this: While in Yellowstone a few years ago, a ranger told me that he had to repeatedly admonish a family for trying to put their 7 year old child atop a bison for a photo op. Go by Buffalo!

Perhaps there should be no barricades at all. I recall a visit to Ireland in the late 90s. They have over there the Cliffs of Moor (sounds rather Princess Bride-like, eh?). The Cliffs are tremendously high and fall hundreds of feet to the sea. The Cliffs also have somewhat wide shelves (ledges) along them, so it is possible for people to climb down to and walk around on the ledges. Height and wind are such on the ledges that some people's vertigo causes them to literally get on their belly and crawl to the edge in order to look over and down to the sea. There is no barricade or fence preventing people from doing this. There is simply a sign saying "Do not go past this sign." My sense was that the laws of Ireland were such that if you were stupid enough to ignore the sign, go down to the ledges and fall off, it was your fault, no one else's so don't trying suing anyone.

Gr8fulted, the Cliffs of Moher that you mentioned were the cliffs used in the Princess Bride as the Cliffs of Insanity.